Dynamite Blasting Research Articles

The Vibration Response to the High-Pressure Gas Expansion Method: A Case Study of a Hard Rock Tunnel in China

The vibration of rock breaking in tunnel excavation may cause serious damage to nearby buildings if it is not controlled properly. With reference to a hard rock tunnel in China, the vibration response to the high-pressure gas expansion method (HPGEM), an emerging rock-breaking approach, was investigated with field tests, theoretical derivations, and numerical simulations, then comparisons with the traditional dynamite blast were performed. Firstly, the vibration velocity prediction formulas of the two methods were fitted based on the field tests. Subsequently, the accuracy of the formula was verified by numerical simulation, and the vibration attenuation law of the HPGEM was explored. Comparisons were made between the blast and HPGEM, particularly the differences in peak particle velocity (PPV) for different agent qualities, distance from the blasting center, and engineering conditions. Furthermore, this study also analyzed the relationship between the agent qualities and the rock-breaking volume under different cases, finding that the HPGEM has slight vibration and good rock-breaking effect. The HPGEM is thus fully capable of replacing dynamite blasting to carry out rock-breaking operations in certain special areas.

Scuba diving-related fatalities in the Philippines from 2008 to 2022 as reported in online news media

The present study aims to investigate the demographics and characteristics of scuba diving fatalities in the Philippines which can help in the identification of local trends and ultimately in the development of appropriate preventive measures. Data on scuba diving-related fatalities in the Philippines from 2008 to 2022 were manually retrieved from online news media sources. Information on age, sex, nationality, certification, purpose, and causative factors, whenever possible were collected and analysed. A total of 39 fatalities were identified having a median age of 43.5 (range 20–80). Majority of victims were males (n = 30), and of foreign ethnicity (n = 26). Asphyxia was identified as the possible disabling injury in almost half of the cases (n = 17). The causes of death based on autopsies were determined only for few cases which included drowning (n = 2), heart attack (n = 1), and traumatic injuries from a dynamite blast (n = 1). Potential vulnerable groups were identified to be the ageing population and foreign tourist divers. In the absence of an existing database, this preliminary report provides the best available evidence at this time concerning scuba diving fatalities in the Philippines.

Work Process and Hazard Analysis in Small-scale Gold Mining in Northern Philippines

Introduction. Small-scale mining (SSM) is mining by individuals, groups, families, or cooperatives with minimal or no mechanization, often in the market's informal (illegal) sector. According to the Mines and Geosciences Bureau (MGB) in the Philippines, the gross production value of small-scale mining as of the 1st to 3rd quarter of 2020 was 0.5 billion pesos (1.05 billion USD).
 Objectives. This study investigated the work process in small-scale mining in the northern part of the Philippines. It documented the occupational hazards that small-scale gold miners are exposed to in each of the work processes.
 Methods. The target population is a community in the northern Philippines where the majority of the males are engaged in small-scale gold mining. This qualitative study used work observation and hazards analysis tools to investigate small-scale miners' work processes and hazard exposures.
 Results. The most widely employed mining technique in the target community is dog-hole mining consisting of several sub-processes: tunneling, ball milling, and gravity concentration, cyanide leaching, and smelting. The occupational hazards identified were noise exposure from the dynamite blast, temperature extremes, and exposure to dust from dynamite blasting. The small-scale miners were subjected to prolonged crouching and bending, handling tools, and carrying heavy sacks filled with mineral ores. The miners resorted to improvised protective equipment such as wearing sleeveless shirts and drinking water for temperature extremes, distancing themselves from the mining blasts during dynamite blasting, and intermittently used carts with manual handling to transport ores packed in sacks. In the ball milling and gravity concentration process, machine-related accidents such as cuts from the crusher were observed. In cyanide leaching, which uses massive amounts of cyanide, the most prevalent hazards were heat, dust, and chemicals such as cyanide fumes. The risks included smoke from burning ore and coal and exposure to borax and nitric acid fumes in the smelting process.
 Conclusion. This study documented the work process in small-scale gold mining and the hazard exposures in this type of informal industry. It is suggested that the local and national governments implement intervention programs for occupational health and safety measures, and social security nets are provided for the small-scale miners in Itogon, Benguet.

(Under)Mining local residential property values: A semiparametric spatial quantile autoregression

SummaryRock mining operations, including limestone and gravel production, have considerable adverse effects on residential quality of life due to elevated noise and dust levels resulting from dynamite blasting and increased truck traffic. This paper provides the first estimates of the effects of rock mining—an environmental disamenity—on local residential property values. We focus on the relationship between a house's price and its distance from a nearby rock mine. Our analysis studies Delaware County, Ohio, which, given its unique features, provides a natural environment for the valuation of property‐value‐suppressing effects of rock mines on nearby houses. We improve upon the conventional approach to evaluating adverse effects of environmental disamenities based on hedonic house price functions. Specifically, in the pursuit of robust estimates, we develop a novel (semiparametric) partially linear spatial quantile autoregressive model which accommodates unspecified nonlinearities, distributional heterogeneity, as well as spatial dependence in the data. We derive the consistency and normality limit results for our estimator as well as propose a consistent model specification test. We find statistically and economically significant property‐value‐suppressing effects of being located near an operational rock mine which gradually decline to insignificant near‐zero values at roughly a 10‐mile distance. Our estimates suggest that, all else equal, a house located a mile closer to a rock mine is priced, on average, at about 2.3–5.1% discount, with more expensive properties being subject to larger markdowns.

The Value-Undermining Effects of Rock Mining on Nearby Residential Property: A Semiparametric Spatial Quantile Autoregression

Rock mining operations, including limestone and gravel production, have considerable adverse effects on residential quality of life due to elevated noise and dust levels resulting from dynamite blasting and increased truck traffic. This paper provides the first estimates of the effects of rock mining — an environmental disamenity — on local residential property values. We focus on the relationship between a house’s price and its distance from nearby rock mine. Our analysis studies Delaware County, Ohio which, given its unique features, provides a natural environment for the valuation of property-value-suppressing effects of rock mines on nearby houses. We improve upon the conventional approach to valuating adverse effects of environmental disamenities based on hedonic house price functions. Specifically, in a pursuit of robust estimates, we develop a novel (semiparametric) partially linear spatial quantile autoregressive model which accommodates unspecified nonlinearities, distributional heterogeneity as well as spatial dependence in the data. We derive the consistency and normality limit results for our estimator as well as propose a consistent model specification test. We find statistically and economically significant propertyvalue-suppressing effects of being located near an operational rock mine which gradually decline to insignificant near-zero values at a roughly ten-mile distance. Our estimates suggest that, all else equal, a house located a mile closer to a rock mine is priced, on average, at about 2.3–5.1% discount, with more expensive properties being subject to larger markdowns.

Addendum: Seeking Hawthorne’s Niagara

Addendum: Seeking Hawthorne’s Niagara

Forensic Identification of Suspected Poached Wild Boar (Sus scrofa affinis)

A case of suspected wild boar death due to dynamite blast by poachers was received by us for confirmation. The skin sample was collected and examined histologically for identification based on hair follicle arrangement in the horizontal section of skin. The horizontal sections of skin from both domestic and wild boar was stained in order to study the distribution of hair follicles. Linear arrangement of hair follicles comprising three primary follicles in a row was observed in both domestic and suspected wild boar. Based on circumstantial evidence it was concluded that it may be belonging to wild boar.

Use of Acoustic Tools to Reveal Otherwise Cryptic Responses of Forest Elephants to Oil Exploration

Most evaluations of the effects of human activities on wild animals have focused on estimating changes in abundance and distribution of threatened species; however, ecosystem disturbances also affect aspects of animal behavior such as short-term movement, activity budgets, and reproduction. It may take a long time for changes in behavior to manifest as changes in abundance or distribution. Therefore, it is important to have methods with which to detect short-term behavioral responses to human activity. We used continuous acoustic and seismic monitoring to evaluate the short-term effects of seismic prospecting for oil on forest elephants (Loxodonta cyclotis) in Gabon, Central Africa. We monitored changes in elephant abundance and activity as a function of the frequency and intensity of acoustic and seismic signals from dynamite detonation and human activity. Elephants did not flee the area being explored; the relative number of elephants increased in a seasonal pattern typical of elsewhere in the ecosystem. In the exploration area, however, they became more nocturnal. Neither the intensity nor the frequency of dynamite blasts affected the frequency of calling or the daily pattern of elephant activity. Nevertheless, the shift of activity to nocturnal hours became more pronounced as human activity neared each monitored area of forest. This change in activity pattern and its likely causes would not have been detected through standard monitoring methods, which are not sensitive to behavioral changes over short time scales (e.g., dung transects, point counts) or cover a limited area (e.g., camera traps). Simultaneous acoustic monitoring of animal communication, human, and environmental sounds allows the documentation of short-term behavioral changes in response to human disturbance.

Frequency and causes of bilateral occular trauma.

To determine the frequency and causes of bilateral ocular trauma. A descriptive case series. Khyber Institute of Ophthalmic Medical Sciences, Hayatabad Medical Complex, Peshawar from October 1999 to September 2006. All patients coming to the hospital with bilateral eye trauma and requiring admission were recruited into the study. The details of patients' demographics, risk factors, ocular examination, treatment offered and final visual acuity were noted and described as frequency and percentages. Out of a total of 1551 patients of hospitalized ocular trauma, 46 (2.9%, 92 eyes) had bilateral ocular trauma. The majority (54.3%) were due to landmine blast injuries followed by dynamite blast in 10.8%, coalmine blast and firearm injury in 6.5% each. Pressure cooker explosion and road traffic accident was the cause in 4.3% each. Gas cylinder and automobile battery explosion, alkali and acid burn, assault and incidental trauma occurred in 2.1%. Sixty three percent were between 16 and 40 years of age. Males were affected in 93.4%. Corneal and / or scleral repair was done in 58.6%, conjunctival and or corneal foreign body removal in 26% and extracapular cataract extraction with intraocular lens implantation in 16.3%. The visual acuity was in the range of 6/60 and perception of light in 54.3%, while in 21.7%, there was no perception of light at the time of admission. Due to severity of injury, the final visual acuity was poor and only 28.2% regained vision between 6/18 and 6/60. In this series, landmine, dynamite and coalmine blasts were the major causes of bilateral ocular trauma. Victims were usually young males. Due to severity of ocular trauma, majority had poor visual outcome.

We've Got a Horn, Let's Toot it

WAS REMINDED this week of a trip took several years ago along a narrow two-lane highway in eastern Kentucky. Traveling these roads always reminds me of childhood trips my family took from Ohio back home to Caney Creek and the cradling safety of the tightly cloistered Appalachians where was born. On this trip, was going to visit Janet, a teacher in what remained of a once-booming coal town tucked into a hollow several miles--and two mountains--from a town large enough to support three motels, a Dollar Store, and a United Mine Workers union hall. My MapQuest directions allotted an hour for the 50-mile drive from the interstate to the school. But knew those miles would be longer and slower than the computer could estimate. It was autumn, and the old-growth forest that survives on those mountainsides had turned from the summer's lush green to every shade of orange, red, gold, and brown. was accustomed to winding roads, but knew that would have to keep a sharp eye on this one. The state road twists precariously close to the mountain's edge and back between narrow passages created by the dynamite blasts necessary to build roads through the massive boulders jutting from the mountainside. As started up the last mountain, it was raining, was behind a coal truck, and fog had reduced visibility to less than a car's length. When my nerves had frayed almost beyond rational thought and my knuckles seemed to have turned permanently white, the road began to level, at least momentarily, and the turnoff to Janet's town came into sight. After a mile, the road took a sharp twist and turned downward into a narrow valley, and the town came into view. The remnants of coal company houses perched along the hillside and the boarded-up buildings along the narrow flat strip of land that led to the creek made it easy to imagine the bustling coal town that existed during the boom days, a boom long past years before Janet was born. drove down Main Street to the school and parked my car in the lot across the street. The building was old, probably built during the Forties' coal boom. crossed the street and walked up the steps to the heavy double door. With each step felt the indentations worn into the bricks by the footsteps of generations of children who had entered the school through this doorway. Inside, found my way to the science classroom. A once state-of-the-art science demonstration table sat at center front. Before it were 36 desks and chairs. In this space, Janet taught science and social studies during the seven 50-minute class periods that make up the school day. Janet and her students had invited me to visit their Earth science class. With very few materials available, Janet had found ways to use the hills and valleys surrounding her school as a learning laboratory. The evidence of the students' work--collections of fossils, animal life, and plant specimens; hand-drawn maps of the region's watershed; research reports; and numerous other projects --lined the window ledges and classroom walls. Talking with these children was almost overwhelming. Their knowledge seemed encyclopedic, and their ability to explain the ways that what they were learning would help them meet Kentucky's rigid state standards was more than impressive. Like many children of cultural minorities, Appalachian children often accept the stereotypes that the larger culture assigns them. But not in this class. One child told me that he used to think that being from the mountains was pretty bad, but now, he said, I think it is cool. This is a good place. As left and headed back across the mountain, was amazed by what I'd seen in that little school. It was only after I'd driven several miles that thought about the role Janet had played during the day. Everything had been about the children--their story, their presentation, their learning. She had all but disappeared into the background. And during our discussions, she had heaped high praise on her students--they had done a great job, almost in spite of her bumblings. …

X-Ray Testimonials in Muriel Rukeyser

X-Ray Testimonials in Muriel Rukeyser David Kadlec (bio) During the earliest and most severe years of the Great Depression, from 1930 to 1931, migrant laborers from Georgia to North Carolina followed word of employment to work-camps near the mouth of a hydro tunnel in the mountains of West Virginia. One of a series of massive hydroelectric projects launched during the 1920s and 1930s, this three-mile conduit had been licensed to divert water from the New River to a nearby power plant, generating “white coal” for both public and commercial use. 1 From its inception in 1924, however, Hawk’s Nest Tunnel had been intended not as a public utility, but as a power source for a new electrometallurgical complex—one owned by Union Carbide and Carbon, the corporate entity that had commissioned the tunnel. 2 With metallurgic processing apparently in mind, engineers and geologists had plotted the tunnel to run through veins of ninety-seven to ninety-nine percent pure silica. 3 During construction, these highly refined mineral concentrations were extracted and sold to the Electro-Metallurgical Company for use in processing steel. Large sections of the tunnel, those that contained the richest deposits, had been widened to maximize profits from in-house transactions (HC, 20, 27, 66). Licensed as a public utility, Hawk’s Nest Tunnel had been drilled as a silica mine. Illicit dry-drilling practices, said to be three times faster than drilling with water, sped the project toward completion, foreclosing a possible shutdown by the Federal Power Commission (HC, 4–5, 59–62, 66). Coupled with substandard ventilation and the contractor’s failure to issue respirators to workers, high velocity drilling had aggravated what industry specialists knew to be a dangerous enterprise. During an epoch [End Page 23] when displaced southern agricultural workers found themselves vulnerable to industrial exploitation, racist divisions of labor facilitated the reckless construction of an “oddly obscure” landmark that still stands as a “marvel of engineering prowess” (HN, 1, 22). Of the 2500 men who worked the tunnel’s interior between 1930 and 1931, a small percentage were white-coal miners and laborers from the nearby town of Gauley Bridge. African Americans, most of them emigrants from southern coastal states, made up eighty percent of this low-paid work force; and they composed an even larger majority of the tunnel’s drillers, nippers, and muckers, workers whose proximity to the drilling-face treated them to the highest concentrations of silica dust. 4 While it is still not known how many black workers were killed by their exposure to the Gauley Bridge tunnel, it was clear to many by the mid-1930s that a large number may have succumbed to industrial disease. Living in segregated, company-owned work camps, and earning subsistence-level wages, black migrant workers in particular lacked the resources to resist hazards that resulted in close to 600 deaths. 5 In late 1935, with rumors of mass graves in West Virginia now circulating in the national press, the New York congressman and labor advocate Vito Marcantonio called for an investigation into allegations of corporate negligence in the suspected silicosis deaths at Gauley Bridge. 6 A group of doctors, journalists, and former tunnel workers arrived in Washington to testify in early 1936. At the congressional hearings mandated by House Joint Resolution 449, a silicotic bench driller named George Robison was asked to testify regarding the working conditions in and around Hawk’s Nest Tunnel. Robison spoke of threats and beatings used by white foremen to coerce black workers back into the mountain after interval dynamite blasts. Reentering the bore within minutes of each shoot, teams of muckers and drillers could see only with difficulty through a white haze of silica (HC, 58, 67). As work resumed at the head, accelerated rounds of dry drilling forced fresh jets of mineral straight back into the faces of workers. Pails of drinking water carried into the shaft looked like buckets of milk. In describing the deathly white residue that coated the tunnel’s interior as well as the “flour-sprinkled” woods around its mouth, Robison treated the white congressional committee to an unsettling image. “As dark as I am,” Robison told...

Seismic experiments on Showa-Shinzan lava dome using firework shots

Seismic experiments were conducted on Showa-Shinzan, a parasitic lava dome of volcano Usu, Hokkaido, which was formed during 1943–1945 activity. Since we found that firework shots fired on the ground can effectively produce seismic waves, we placed many seismometers on and around the dome during the summer festivals in 1984 and 1985. The internal structure had been previously studied using a prospecting technique employing dynamite blasts in 1954. The measured interval velocity across the dome in 1984 ranges 1.8–2.2 km/s drastically low compared to the results (3.0–4.0 km/s) in 1954; in addition, the velocity is 0.3–0.5 km/s higher than that in the surrounding area. The variation of the observed first arrival amplitudes can be explained by geometrical spreading in the high velocity lava dome. These observations show a marked change in the internal physical state of the dome corresponding to a drop in the measured highest temperature at fumaroles on the dome from 800°C in 1947 to 310°C in 1986.

The Relationship Between Rockfall and Shocks from Blasting

The relationship between rockfall and vibration of the ground has never been fully analyzed before in Japan because of several problems which fall within one of two categories which we have labelled “motivecause” and “primary cause”.Problems falling within the “motive cause” category are concerned with characteristics of vibration whilethose problems falling within the “primary cause” category are concerned with the conditions of mountainslopes (e. g. morphometric parameters of slope; shape, size and depths at which blocks have been buried onslopes ; quality of weathered materials and surface soil).In spite of these problems, it is quite important to analyze the relationship between rockf all and vibrationof the ground for some kinds of construction works such as railway and tunnel construction because shocksfrom blasting may cause rockfalls.In our survey, two seismic tests were carried out-one involving a dynamite blast and the other involvinga shockwave caused by a passing train.The results of these tests can be summarized as follows:1. The shock that was produced by the passing train did not cause a severe rockfalls. The maximum deformationof the ground was 7.6-10-5 cmand occurred above 10 seconds. These results are too small tocause a rockf all.2. The relationship among the amount of dynamite, the maximum displacement, the maximum accelarationand the transmissive velocity of vibration was studied to find the point at which a severe rockfall waslikely to occur during tunnelling work.In this test, 3 kg of dynamite were exploded 50 meters from the test site. As a result, the maximumdisplacement was 1.4-10-3 cm. This value is also too small to cause a rockfall.

Influence of cyclic load input on the mechanical properties of a sensitive soil from Orleans, Ontario

The importance of disturbance and remoulding to the alteration of mechanical properties of sensitive soils has been well documented in the geotechnical literature both in terms of laboratory and field behaviours. Man-made transient dynamic input such as dynamite blasting, heavy vehicles, and train movement have been suspected of being capable of causing a reduction in the in situ strength parameters of sensitive clays. A laboratory test program was undertaken to determine whether dynamic loading at peak stress levels below normal failure strength caused similar changes in the mechanical properties, and specifically to quantify the phenomena.In order to simulate highly overconsolidated conditions most of the tests were carried out under conditions of no confining pressure, although supplemental data were obtained from consolidated undrained tests. Some of the variables examined in this program were confining pressure, mean deviatoric stress, cyclic deviatoric stress, cyclic strain, number of applications, frequency, and reference strength. In order to compare the effect of dynamic input with the long-term creep phenomena, a simultaneous constant load program was undertaken.In general terms, the study indicates that under the prestated laboratory test conditions no major reduction in peak strength was found under dynamic loading, and that failure would occur at comparative stress levels under dead-load conditions, but required a greater time. In addition, examination of the sample after failure revealed that any remoulding of the sample appeared to be restricted to the area adjacent to the shear zone.

Experimental determination of damping in nuclear power plant structures and equipment

A summary of damping values for structures and equipment obtained in several full-scale dynamic tests performed on a research reactor, three experimental power reactor plants, and a commercial power reactor plant is given. The testing techniques used include steady state shakers, dynamite blasting, and snapback. In an appendix, guidelines are presented for required frequency resolution and record length for damping estimation from blast or snapback records. The influence of system non-linearity upon damping interpretations is also discussed.

Simulation of strong motion earthquake effects on structures using explosive blasts

This paper presents the results of three separate test programs which were conducted to determine the feasibility of simulating strong motion earthquake effects using dynamite blasting techniques. The three programs measured blast induced structural responses at: (1) the UCLA Field Station; (2) the Enrico Fermi Nuclear Power Plant, Monroe, Michigan; and (3) the experimental gas-cooled reactor facility (EGCR), Oak Ridge National Laboratory. The evaluation of the tests indicates that the simulation of strong earthquake excitations using subsurface blasting techniques is a valuable testing tool. Each of the three discussed tests indicate that reliable estimates of natural frequencies and mode shapes of vibration can be obtained directly.

Double-Flash Microsecond Silhouette Photography

Equipment is described to take double-exposure silhouette photographs of rapidly moving objects. Each exposure time is about ⅕ microsecond, and the time interval between flashes is adjustable. An eight-inch square Ektalite Fresnel lens is used as a field lens to focus the light from the illuminating spark into the camera lens; it is especially useful for subjects where the lens is frequently damaged. Timing of the first spark is conveniently made for explosions by a photoelectric tube triggered by the light of the explosion. A double exposure photograph of a dynamite blasting cap is given as an example.

COMPARISON OF FIELD AND LABORATORY MEASUREMENTS OF SEISMIC VELOCITIES IN SEDIMENTARY ROCK

In the field, a small dynamite blast was found satisfactory as the source of both longitudinal and transverse waves. Motion thus generated was detected by a single three-component seismometer, successively positioned at different horizontal or vertical distances from the shot point. With vacuum-tube amplifiers and a galvanometer-type, recording oscillograph, the three principal components of particle motion were recorded on photographic paper as a function of time. Analysis of these records for wave types and wave paths yielded the field observations of velocity. After the wave path of the field measurements was established, cores from relevant parts of the section were studied in the laboratory. Samples were machined to the form of a right circular cylinder and their resonant frequency for forced vibrations in logitudinal and torsional modes determined. The effect on these resonant frequencies of the variables: water content, pressure, and temperature as well as measurement frequency and amplitude was determined, so that conditions of laboratory velocity measurements could be corrected to those of the emplaced rock. In Osage County, Oklahoma, four attempts to identify transverse body waves by shooting vertical profiles with a three-component seismometer on the surface and the shot at varying depths in an abandoned hole were unsuccessful. Evidently, the fraction of detonation energy delivered to body shear waves was exceedingly small in comparison with that delivered to other extraneous motions. Vertical profile shooting was abandoned in favor of horizontal profiles. In Section 2, T.25N., R.4E., Osage County, Oklahoma, velocities of: V P = 9200 ± 300 ft/sec. V s = 5000 ± 200 ft/sec. were measured in an upper layer of Permian sand and shale, approximately 250 feet thick, and: V P = 14,000 ± 400 ft/sec. V s = 9900 ± 300ft/sec. in a lower, inhomogeneous layer of limestone. After correcting to the most probable conditions of water content, pressure, and temperature for the rock, in place, 17 core specimens from 8 closely spaced horizons in the lower limestone gave a bimodal distribution of laboratory velocities with the modes: ![Formula][1] Conclusions are: (1) Transverse elastic body waves of the SV type can be generated by a small dynamite blast in sedimentary rocks if the shot hole is shallow and high confining pressures are avoided. (2) The velocity of an SV type body wave can be determined with approximately the same accuracy as a longitudinal type body wave. The transmission path is subject to greater uncertainties. (3) Among the independent variables affecting velocities in a near-surface, Permian limestone, water content is the most important. Pressure, temperature, and measurement direction, amplitude, or frequency have relatively minor effects. (4) The Neva limestone may be subdivided on the basis of density and laboratory determinations of velocity into two distinct types of alternating microlayers with thickness of the order of 1 foot. (5) Under the conditions of this work, elastic parameters and Poisson's ratio computed from field measurements differ significantly from values determined by laboratory measurement. [1]: /embed/graphic-1.gif

Fourier analysis of a blast record

This paper reports the Fourier analysis of a seismogram of a dynamite blast recorded by a Taylor‐Macelwane seismograph. The first six harmonics were calculated for 26 sections of the record. The errors inherent in such an analysis are discussed.

A three‐component portable seismograph for the measurement of vibrations

General Features—This instrument was designed and constructed primarily for the registration of vibrations from dynamite blasts, traffic, machinery, and general Industrial sources. For vibrations of a frequency of three cycles per second or more, it gives a record directly proportional to displacement. With a magnification factor of 25 over this range, it gives clear, full registration from about 0.0005 to 0,035 inch. The maximum on‐scale displacement which can be recorded usefully on any one of the components is 0.080 inch. Over a period of 15 years, experiments have shown that these constants are best adapted to the service for which this was designed.