Hot Water Flow Research Articles

Geothermal systems ancient and modern: a geochemical review

Geothermal systems occur in a range of crustal settings. The emphasis of this review is on those occurring in regions of active or recently active volcanism, where magmatic heat at depths up to 8 km leads to convection of groundwater in the upper crust. Hot water (and steam) flows are controlled by the permeability of the crust and recent data have emphasised the dominance of secondary permeability, especially fractures. Drilling to depths of up to 3 km in these systems encounters near-neutral pH alkali chloride waters with temperatures up to about 350°C and chloride contents generally in the range 500 to 15,000 mg kg −1 although much higher salinities are encountered in some systems such as in the Imperial Valley, California. Stable isotope studies indicate the predominance of a meteoric source in the majority of geothermal systems although seawater predominates in some regions, such as Reykjanes, Iceland. Mixing of waters from both sources also occurs in some systems and some magmatic fluid may also be present. The major element geochemistry of geothermal fluids is determined by a set of temperature-dependent mineral-fluid equilibria although chloride and rare gas contents appear to be independent variables reflecting the sources of these components (sedimentary or volcanic rocks, seawater, magmatic fluids, etc). Boiling in the upper portion of geothermal systems is accompanied by the transfer of acidic gases (CO 2 and H 2S) to the resultant steam which may penetrate the surface as fumarolic activity or become condensed into shallow groundwaters giving rise, with oxidation, to distinctive low pH sulphate bicarbonate water. Fluid inclusion, stable isotope and mineral alteration studies have led to the recognition in many Tertiary hydrothermal ore deposits of physical and chemical environments analogous to those encountered in the present-day systems. The vein-type gold-silver, Carlin-type gold and porphyry-type copper-molybdenum deposits of the western United States are particularly well studied examples. Sub-ocean floor equivalents of the terrestrial geothermal systems have been recognized in ocean floor spreading centres such as the East Pacific Rise and deep-sea submersible vehicles have allowed visual observation of sea floor hot springs actively depositing metal sulphides. These environments may parallel those of the Cyprus-type massive sulphide depositing systems, while sub-sea floor systems of the type responsible for Kuroko-type massive sulphide deposits may eventually be encountered in island are settings.

Using Microprocessors to Save Energy

As the cost of fuel rises, so the need to economise on its use becomes more important. In industry, fuel is used not only to drive machinery but also for heating industrial premises (and sometimes for cooling, for example in cold stores and in hot climates). Considerable saving of fuel used for heating, or for cooling, can be achieved by means of new technological innovations, in particular the use of microprocessors to control temperatures as well as the flow of hot water or cold or hot air.

Numerical Simulation of Laboratory Steamflood Experiments

Abstract The Petroleum Recovery Institute has operated a scaled steamflood physical model since 1975. The objective of this work was to define and to evaluate the capabilities and limitations of Intercomp Ltd. "s numerical steamflood simulator and the Petroleum Recovery Institute"s physical model. Three different types of laboratory experiments were selected for numerical history matching-waterflood, hot-waterflood and steamflood. The objective was to match oil, water and steam production as well as the energy balance and temperature profiles, using a single set of physical and petrophysical parameters. In addition, sensitivity studies were computed for three different grid systems, specifically a coarse cross-sectional grid (8xlx4), a fine cross-sectional grid (l6x1x8) and a three-dimensional grid (9x5x4). Excellent matching was obtained for the fluids production and for the energy balances. However, some, difficulties were encountered during attempts to match some of the temperature profiles, especially those associated with the flow of hot water along the bottom of the reservoir. As a result of the simulations, new measurements of thermal conductivity between the model and the underlying concrete bed were performed. A more complete interpretation of the physical model was obtained. The results indicate that physical model experiments offer useful data which can enable testing and calibration of numerical models, while the latter can help in obtaining a more precise description of the former. Therefore, the physical and numerical models should be used in a mutually complementary manner. INTRODUCTION Numerical simulators for steam injection oil recovery processes are being used frequently by reservoir engineers especially in the three areas of history matching(1–6), sensitivity studies(6–7) and field design and prediction(8–10). However, numerical simulators are complicated reservoir engineering tools and one has to realize their capabilities and limitations in order to use them properly. The successful design of any enhanced oil recovery process requires that one be equipped with a reliable set of reservoir data which includes geological, physical and petrophysical properties. History matching with a numerical simulator is often used to verify the parameters that have been obtained from laboratory measurements, well logs or by correlation. Typically, it is difficult to obtain a unique result from history-matching studies of field-derived performance data because a large number of parameters, involved in the calculations, must be either estimated or determined indirectly. History matching of laboratory steam flood experiments provides a better insight into the numerical simulator"s capabilities, because one has better control over most of the parameters defining the system. An additional advantage of history matching laboratory data is that more experimental data, usually of higher quality, are available to enable comparison with numerical results. The PRI Research Division has been studying steamflood oil recovery processes using a one-twelfth of an inverted seven spot, partially scaled physical model(ll.12.l3) since 1975. Some sixty experimental runs have been made to date for various steam injection rates, steam qualities, initial water saturations and oil characteristics. Three of these runs were chosen for this study – a cold-waterflood, a hot-waterf1ood and a steamflood. (Figure in full paper) Physical Model Apparatus The experimental apparatus is shown schematically in Figure 1.

Thermal structure of the yakedake volcano, Japan: Karukaya and Takara geothermal areas

Abstract The hydrothermal water balance and the thermal structure of Yakedake volcano and its vicinity are considered quantitatively. The hydrothermal activity is intense in the valleys at the western foot of the volcano and the Nakanoyu area. The total hot water flow from the discharge area amounts to 2.07 × 10 4 1/min , about 60% of which discharges from the Shinhodaka area alone. There are some large basins (Abodaira and others) in which the rocks are mainly tuff breccia and volcanic products showing very high permeability for water. The total area of the water recharge zone amounts to 18.2 × 10 6 m 3 . A model for the hydrothermal system within Yakedake volcano is proposed and from the results of boreholes, the thermal and geological structures of the Karukaya and Takara geothermal areas are also presented. Attempts were also made to estimate the subsurface temperature distribution from the observed near-surface ground temperatures. Results of three-dimensional conduction model calculations indicate that the subsurface temperatures are high in the central part of the crater and in the areas with self-flowing springs along the rivers. The obtained isotherms encircle the volcanic center of Yakedake.

Geothermal exploration in the azores: 180/ 160 in calcites from volcanic rocks

The oxygen isotope composition of calcite veins and vugs in basalts from a drill site on the island of Sao Miguel show near-equilibration with fresh water at observed temperatures only at a depth of 600–700 m. This is interpreted to mean that the greatest flow of hot water may be occurring in this depth interval.

Functional Analysis of a Thermal Spring Ecosystem, with an Evaluation of the Role of Consumers

Low temperature (< 40 degrees C) alkaline thermal spring effluents in Yellowstone National Park support a benthic algal—bacterial mat fed upon by a single herbivorous brine fly (Diptera: Ephydridae), which in turn is consumed by a number of arthropod predators (water mites, spiders, and a predaceous fly). A census of an entire spring ecosystem provided a framework upon which to integrate present knowledge of this system. Growth of the algal—bacterial mat appears to be nutrient limited; measures of free CO2 concentrations are good predictors of the differences in productivity within and among springs. Paracoenia turbida, the herbivore, saturates all suitable oviposition sites, and its larvae destroy all algae available below them. The larvae apparently suffer substantial density—dependent mortality late in their development, when they consume algal dams protecting them from hot water flows. Thus, they compete for limited space of suitable temperature. Algal—bacterial biomass persists because, at any one time, most of the mat is too hot for larvae, or is covered by flowing water and consequently unsuitable for oviposition. The brine fly eggs which constitute the prey for most predators are also largely unavailable because the flies insert them into the algal—bacterial mat, where they are difficult to remove and feed upon. The demand—availability ratio for fly eggs is high; therefore reproduction of the major predatory water mite, Partnuniella thermalis (Hydrachnellae) is probably limited by the supply of available eggs. Despite the abundance of their prey species, then, both primary and secondary consumers seem to be resource limited because most of their prey are unavailable. The important role of refuges in defining the biomass structure of this ecosystem prompted us to define four conditions which tend to limit consumer influence on prey density: (1) evolutionary specialization by consumers, which narrows the spectrum of potential foods (2) poor food quality which does not allow population growth; (3) evolved defenses of the prey; (4) the degree of uncertainty in resource distribution in space or time. Restrictions of type (4) are difficult in document and may often go unappreciated, but an example from the thermal spring system shows the uncertainty in resource distribution may be evolutionary insoluble, and it may be a powerful constraint on consumer impact. There is little reason to believe that these conditions are any less powerful in complex than in simple systems. By analogy then, the ability of consumers to influence prey density in complex terrestrial and aquatic systems may also be severely limited. The importance of refuges in complex systems might be inferred from measurements of community responses to low—level enrichment or harvesting. Even though their direct influence on prey densities is limited, consumers in the thermal spring ecosystem increase the net primary production of the system and increase the efficiency of energy transfer between the first and second trophic levels. Thus, they affect processes, not prey densities, in this system.

Holst Filtration Apparatus for Van Soest Detergent Fiber Analyses

Abstract New filtration equipment was developed to improve the acid-detergent method of fiber fractionation. This apparatus incorporates a vacuum manifold with an air metering device that provides the operator very precise control over the partial vacuum, permitting a very gradual change in vacuum level as needed for proper filtration. The partial pressure is provided by a water aspirator. A hot water jacket permits a continuous flow of hot water around the sample during the filtering process to keep the sample hot. This speeds filtering on practically all samples and is essential for reliable results on samples high in carbohydrates and salts. As a result of this new filtration equipment we do not need asbestos for a filter aid. This eliminates the need for duplicate acid-detergent fiber analyses when using 72% H2SO4 for the cellulose and lignin determinations. Six independent analyses were performed on each of 9 samples (3 feces, 3 orts, and 3 feeds) for the determination of acid-detergent fiber and its constituents. The average maximum differences for these analyses indicate that this filtration apparatus and the method are reproducible and have reduced the filtration time from several hours, on some samples, to 15 min.

A nonelectrical incubator for developing countries.

A nonelectrical human incubator for premature infants has been designed and built for use in rural areas of developing nations where electricity is not readily available. This incubator may be operated using kerosine or gas as the source of energy. The unit uses an automatic self-activating regulator which controls the flow of hot water through a simple heat exchanger; the air in the incubator is heated by natural convection, and the humidity is adjusted by water evaporation. The temperature inside the incubator can be maintained to within±0·3°C of the desired level. The unit operates for extended periods of time with little or no supervision.

Optimal operation of a tubular chemical reactor

AbstractA theoretical and experimental study was conducted on the optimal steady state operation of a jacketed, tubular, liquid‐phase reactor in which consecutive second‐order reactions occurred in turbulent flow. To verify the proposed mathematical model, diethyl adipate was saponified with sodium hydroxide in aqueous solution. The 150 ft. long reactor jacket was divided into 5, 30 ft. sections. Hot water flow rates in the jacket sections were chosen to maximize the concentration of monoethyl adipate ion at the reactor exit. The plug‐flow model and a position‐dependent heat transfer coefficient accurately described temperature and concentration profiles. The Pontryagin maximum principle was used to choose idealized reactor temperature and wall heat flux profiles which would maximize the exit concentration of monoester. The maximum principle was shown to be an effective tool for this type of reactor optimization. A technique is given for optimizing more complex reaction systems.

Chemical indicators of subsurface temperature applied to hot spring waters of Yellowstone National Park, Wyoming, U.S.A.

Under favorable conditions the chemistry of hot springs may give reliable indications of subsurface temperatures and circulation patterns. These chemical indicators can be classified by the type of process involved: Indicator Dominant Process The silica geothermometer Solution-precipitation Alkali ratios Ion exchange Cl/(HCO 3 + CO 3) ratio Rock alteration by dissolved CO 2 Relative concentration of Partitioning owing to subsur- volatiles in spring water face boning All these indicators have certain limitations. The silica geothermometer gives results independent of the local mineral suite and gas partial pressures, but may be affected by dilution. Alkali ratios are strongly affected by the local mineral suite and the formation of complex ions. Carbonate-chloride ratios are strongly affected by subsurface P CO2. The relative concentration of volatiles can be very misleading in high-pressure liquid systems. In Yellowstone National Park most thermal waters issue from hot, shallow aquifers with pressures in excess of hydrostatic by 2 to 6 bars and with large flows (the flow of hot spring water from the Park is greater than 4000 liters per second). These conditions should be ideal for the use of chemical indicators to estimate aquifer temperatures. In five drill holes aquifer temperatures were within 2°C of that predicted from the silica content of nearby hot springs; the temperature level off at a lower value than predicted in only one hole, and in four other holes drilling was terminated before the predicted aquifer temperature was reached. The temperature-Na/K ratio relationship does not follow any published experimental or empirical curve for water-feldspar or water-clay reactions. We suspect that ion exchange reactions involving zeolites in the Yellowstone rocks result in higher Na/K ratios at given temperatures than result from feldspar or clay reactions. Comparison of SiO 2 and Cl/(HCO 3 + CO 3) suggest that because of higher subsurface P CO2 in Upper Geyser Basin a given Cl/(HCO 3 + CO 3) ratio there means a higher temperature than in Lower Geyser Basin. No correlation was found in Yellowstone Park between the subsurface regions of highest temperature and the relative concentration of volatile components such as boron and ammonia.

The control and safety of geothermal installations

Every geothermal bore will have its own individual characteristic relating mass flow and pressure, and no two bores will behave in exactly the same manner. In a ‘wet’ field a third variable, the dryness fraction, is added to the pressure and the mass flow as a component element of the bore characteristic. Where several bores simultaneously supply geothermal fluids to a utilisation plant, whether for power generation or other purpose, it is necessary to devise a system of control whereby the bores, despite their different characteristics and allowing for possible changes in these characteristics, will collectively provide the required quantities of fluids at the required pressures and with a minimum of waste, and whereby any unwanted fluids are automatically disposed of. In a complex system of transmission and plant, there may be points at which the prime necessity is to supply a certain quantity of steam and where pressure must be permitted to vary in such a manner as to ensure this supply. At other points the prime necessity may be constancy of pressure and the quantity of steam delivered to the plant must be permitted to vary in such a manner as to ensure this constancy. The transmission of hot water, collected at saturation pressure, must be effected without permitting the water to boil, as this could give rise to unpredictable and possibly disastrous water hammer phenomena. To ensure this, an adequate system of controlling the rate of hot water flow is necessary, taking due account of pipe friction, gradient and accelerations (both positive and negative). In addition to these requirements for controlling the flow of geothermal fluids, both steam and hot water, in such a manner that the utilisation plant may function smoothly and correctly, precautions must also be taken to control these fluids so as to prevent damage to plant and injury to personnel as a result of the bursting of pipes or pressure vessels on account of excessive pressures or their collapse under vacuum conditions, or as a result of water hammer arising from entrained water in the steam mains. All these requirements call for adequate automatic controls and safeguards, which are described in the paper. There will also be a need for conditions at certain points in the plant and in the field to be monitored at a central control point, to enable the plant operators to observe what is happening from afar and to take corrective action in emergencies by means of remote control.

Development of a theory of the wairakei geothermal field by the 《 simplest cases first 》 technique

The theory is required to relate the pressure at depth in the geothermal field to the history of hot water discharge, to enable prediction and control of the performance of the field. The history, in brief, is that as the total discharge through bores increased during the past fifteen years to about five times the natural discharge rate, the pressure 2200 ft (670 m) below the surface fell from about 900 psig (62 bar) to about 600 psig (41 bar). The aim has been to discover the simplest theory which will relate pressure to discharge, in the hope that some of the phenomena which are undoubtedly occurring may nevertheless be having a negligible effect on the pressure. It was shown first that no hydrostatic theory could give results consistent with observed pressures. These pressures implied the presence of an upward potential gradient, and the first hydrodynamic models tried, chosen to have the simplest possible form, assumed a rising, vertical, axi-symmetrical column of hot water which remained as pure liquid phase right to the ground surface, and assumed quasi-steady flow at three particular dates. Such models, on being fitted to observational data, gave results consistent with the hypothesis that convective buoyancy forces cause the upward flow of hot water. The results also showed that, contrary to the original assumption drawdown of the liquid surface would occur, beginning in 1959 which was in fact the date at which pressure first began to fall rapidly. The basic picture is that the bore discharge is being supplied from a number of directions: from lateral inflow of cold ground water, from increased upward flow of hot water, which comes ultimately from lateral inflow at greater depths, and also from drawdown from the surface.

Geochemical studies of thermal waters in the Southern Lowlands of Iceland

The data on underground temperatures and underground flow of hot water in the low temperature area of the Southern Lowlands, Iceland, which are presented here, are almost exclusively based on studies of the chemical composition of the thermal waters. The hydrothermal area is one of the two largest low temperature areas in Iceland and covers an area of some 700 km 2. Total discharge from thermal springs is about 330 litres/sec and from drillholes about 120 litres/sec. The hydrothermal area is located in basalt lava flows, hyaloclastites, and some shallow water sediments of recent age. The thermal waters have characteristically high pH and are notable for their low content of total dissolved solids as in fact thermal waters from other low temperature areas in Iceland. The waters are saturated with respect to the solubility of calcite. The concentrations of calcium and fluoride are of the order expected for the solubility of fluorite. Magnesium concentrations are very low. Thermal waters issuing from marine sediments contain higher concentrations of chloride and calcium than thermal waters issuing from basaltic rocks. The ratio of Cl/B in the thermal waters falls into three geographically separate groups suggesting that there are three hydrothermal systems in the area. The ratio of Na/K in the thermal waters increases when silica decreases. For a particular rock type this increase is mostly caused by potassium depletion. It seems likely that such potassium depletion is caused by reactions with montmorillonite and albite. However, these reactions may be governed principally by temperature. The amount of silica in the thermal springs reaches a maximum in the northern part of all three hydrothermal systems and decreases southwards. Temperatures of last equilibrium with quartz reach a maximum of 160°C in the westernmost systems and 178°C in the easternmost hydrothermal system. Experience from several other hydrothermal areas in Iceland has shown that temperatures of last equilibrium with quartz are not much lower than temperatures found by drilling to depths of some 1000 metres. Therefore deep drilling for steam in this area is not feasible.

A new technique for measuring thermoregulatory behavior in the rat.

A tracking procedure was used to investigate the ability of rats to regulate their ambient temperature. Rats were placed in a chamber with two levers; depressions of one lever controlled a cold-water flow (11 degrees C) and the other controlled the flow of hot water (57 +/- 1 degrees C). If it alternated responses, the rat could regulate temperature within these two extremes. With training, this regulatory behavior resulted in a narrow environmental temperature range that approximated normal body temperature.

Results of a Tertiary Hot Waterflood in a Thin Sand Reservoir

Abstract This paper presents and discusses the results obtained daring a pilot test in the Loco field in southern Oklahoma. The test was conducted in a 2 1/2-acre pattern that was part of a 20-acre conventional waterflood pilot area. The conventional flood was well past its economic limit when the hot waterflood was initiated to obtain technical information from and operating experience in a reservoir containing 600 cp oil. Temperature data from nine observation wells showed that about 75 percent of the pattern was affected by heal, and that heat losses were severe in the pilot pattern. About 60 percent of the injected heat was lost to overburden and underburden zones during hot-water injection. Wellbore heat losses were held at tolerable levels at the shallow depth of the test by providing a low-pressure air annulus between the injection tubing and well casing. Hot water provided water injectivity increases of 200 to 400 percent. The hot water channeled across the lower portion of the oil sand in three directions through zones of relatively high water saturation. There was no conclusive evidence that natural fractures or pressure partings affected the flow of fluids in the pilot pattern; however response undoubtedly was affected by localized pressure and by injection-production rate ratios. The results snowed that hot waterflooding increased oil recovery. The total tertiary oil production from the pilot pattern area was 3,896 bbl or about 156 bbl/acre-ft swept by neat. The corresponding WOR was about 34:1. Description of the Hot Waterflood Process To hot waterflood an oil reservoir, water is injected that has been heated to a temperature substantially higher than the original reservoir temperature, but lower than the vaporization temperature of water at the prevailing pressures. In the reservoir the hot water flows continuously into cooler sand and rapidly loses heat to the sand until it has been cooled to the original reservoir temperature. Thus, a heated zone and a region or "bank" of cooled water begins to accumulate immediately after hot water injection is started. This bank of cooled water continues to grow ahead of the heated zone, which also grows, but at a slower rate. This occurs because heat transfer is almost instantaneous, and the ratio of heat capacities of water to rock is such that two or three unit PV of hot water must be injected to heat a given unit bulk volume of the reservoir. The primary displacement mechanism is the same for both hot and conventional cold waterfloods; i.e., "piston" displacement occurs at the original reservoir temperature. The incremental benefits of hot waterflooding usually occur long after the breakthrough of cold water at producing wells, and the increased oil recovery necessarily is accomplished with high WOR's (water-oil ratios). Heat decreases the viscosity and density of oil and water. These effects result in more rapid and increased recovery of secondary or tertiary oil. If the cost of the required heat is low enough, the ultimate oil recovery of a hot waterflood should be increased substantially over what would be expected at the economic limit of a conventional cold waterflood. The economic benefits of any hot-fluid injection project depend primarily upon the cost of the heat required to produce more oil at an increased rate. This cost depends in part upon the amount of heat lost to surrounding formations. Heat loss depends upon reservoir thickness, water injection rate and temperature, the depth of the formation. well spacing, and the characteristics of the reservoir rock and surrounding formations. In general, percentage heat losses decrease as injection rate and reservoir thickness increase. Although it is an old idea, hot-water injection has not received widespread field application in the oil industry as a drive process. Much of the original field work with hot water was done in Pennsylvania fields where water permeabilities and injection rates are low. In these cases, hot-water injection was used primarily as a means of increasing injectivities - not as a recovery process. Ramey recently has published an excellent review of the development of hot fluid injection processes. Recent publications and our own experiences now indicate that hot water or steam injection also can effectively increase the oil recovery from reservoirs containing viscous crudes. However, the economics of these methods as displacement processes have not been established. JPT P. 739ˆ

A Special-Purpose Controlled-Environment Unit

A controlled-environment unit consisting of eight chambers is described. An attached darkroom and enclosure of the chambers in a darkroom allow experiments in the physiology of flowering. Temperature range (from below 0⚬ C to 45⚬ C or more) and light intensities (2,000-5,000 ft-c) allow limited experiments in physiological ecology. Temperature is controlled by modulating the rate of flow of chilled brine or hot water: through coils in each chamber. Exceptionally large cooling coils and the brine system offer some special advantages. For example, freezing temperatures may be obtained in the chambers without frosting the coils (provided brine temperature is as high as possible), and the coils do not remove excessive moisture from the air. Accurate humidity control is yet to be achieved. The lighting system is a conventional one, consisting of mixed fluorescent and incandescent light. Separation of the lights from the chambers by a layer of plastic is essential for proper control of lamp ambient temperature. Plastic also results in nearly double the flowering response in Xanthium. Special light sources for high-intensity light and other special features are mentioned.

Fluid Flow Through Two Orifices in Series: III—The Parameters of Metastable and Stable Flow of Hot Water

Abstract The flow of hot water, with saturation pressure above the downstream pressure, through orifices or nozzles depends largely upon the nature of the expansion of the fluid and the confinement of the expansion by the orifice or nozzle. Intermolecular forces as influenced by surface tension tend to metastabilize the initial liquid phase to a corresponding subsaturated pressure. These forces also tend to metastabilize the droplets formed in steam at the critical size corresponding to the critical pressure at expansion. The influence of orifice or nozzle form on the expansion process for initially stable and metastable entering fluid is analyzed with confirming test data interpreted from the intermediate-pressure measurements between two identical orifices in series. Control effects obtainable with change of the intermediate pressure between two orifices as determined by the thermal state of the fluid are briefly discussed and a new practical application form of such a control element as applied to condensate removal from steam systems is described. Attention is directed toward new avenues for further investigation in this field.

Closure to “Discussion of ‘Fluid Flow Through Two Orifices in Series: III—The Parameters of Metastable and Stable Flow of Hot Water’” (1957, Trans. ASME, 79, p. 189)

Closure to “Discussion of ‘Fluid Flow Through Two Orifices in Series: III—The Parameters of Metastable and Stable Flow of Hot Water’” (1957, Trans. ASME, 79, p. 189)

Geology: The Geology of Thrace

DR. A. BOUÉ, who has been investigating the geology of Thrace, announces some of the results of his expedition. He has traced the cretaceous and nummulitic formations from Jarim Brugas to Adrianople, and found crinoids in the shales and limestones near Eski Sara, one of which he is inclined to identify with the carboniferous limestone. The steep southern declivity of the Balkan represents a great fissure of dislocation, the granitic central stock of the ancient Balkan having sunk down odily during the enormous porphyritic and trachytic eruptions; hot water flows from the fissures of the sunken granite, and forms numerous baths along the foot of the Balkan. In Mechli ravine, near Kisantik, immediately surrounded by mountains 4,000 feet in height, Dr. Boué discovered, resting directly upon gneiss, an old carboniferous formation, with three beds of good coal; but as no fossils were to be detected in the deposit, he was unable to determine whether it belongs to the coal measures. Coal-beds, probably of Eocene age, occur in the Rhodopi.—[Proc. Imp. Geol., Institute of Vienna, 31st Oct., 1869.]

On a New Thermostat for Regulating Ventilation

Mr. Ward said—Having been engaged in horticultural pursuits, he had found that it was desirable to have some instrument for regulating the ventilation and temperature of hothouses, without requiring the close attention of the gardener. He then described the invention which he calls a Thermostat, and which consists of metallic vessels, in which the vapour of a volatile liquid is used to give motive power for opening or shutting ventilators, or dampers, or regulating the flow of hot or cold water, or similar applications for regulation of temperatures. The vapour of aether has been used for such purposes when confined in tubes by mercury, but in such apparatus the amount of power to be obtained is much limited by the weight and consequent expense of mercury required. He makes use of vessels of thin metal, of which the ends or sides being discs of metal, are so thin and flexible as to be changeably either convex or concave, and in which the vapour of sulphuric aether (or of suitable volatile liquid), along with a portion of such liquid, is enclosed; the discs or ends of such vessels acting as diaphragms, separating the vapour from the external atmosphere, will, at temperatures under the boiling point of the fluid employed, be pressed inwards by the atmosphere, but with a pressure varying according to the temperature. He therefore attaches a counterpoise of sufficient weight partially to counteract the pressure of the atmosphere, so that the differential pressure of the aethereal vapour above ...