Wide Halo Research Articles

Geophysical characteristics of geosynclinal regions

The different parts of modern geosynclines, such as the zones of central uplifts, internal zones and external zones or orogenic regions, have typical geophysical characteristics which signify the specific deep structure of the crust and the upper mantle in these regions. A wide halo of geosyncline influence upon the adjacent areas indicates that the sources of geosynclinal activity lie deep in the earth's upper mantle. Geosyncline periphery is a frontal zone where processes and movements in the substance of the upper mantle are especially strong at present.

The Focalograph

MANY methods have been proposed for the examination of the target of an x-ray tube. It must be conceded that any method which provides a permanent record for comparison has advantages over methods which do not have this feature. The device described, the Focalograph, as proposed by Sergeant Black is a simple, economical, and efficient apparatus for: (a) Providing a record of the appearance of the target of a roentgen tube. (By enlargement obtained by increasing the grid-film distance it is possible to see minute defects plainly.) (b) Demonstrating the effect of angular position of the target of a roentgen tube upon the effective ray. (c) Checking the effective area, actual area and minimum projected area of the focal spot of a roentgen tube. This is especially valuable in checking performance of tubes against specification claims. (d) Determining the maximum ray divergence and minimum focal film distance for various types of tubes as they are affected by the angle of the target face. The apparatus described consists of a simple wood-constructed tube holder for the roentgen tube with a special accurately perforated lead diaphragm placed on an arc between the tube and a film which is to be exposed for record (Fig. 1-A). It is also possible to study the lateral divergence by use of grids constructed in that plane. It is conceivable that many methods of grid construction may be applied to the basic apparatus in the future. The grid shown is the best found as yet for comparison studies, as it is possible to obtain several exposures on the same film. The tube is enervated from a regular x-ray machine in the usual manner. The arc of the film and of the lead diaphragm is so constructed that the appearance of the film exposed is the same as the composite image obtained by many horizontally placed films exposed with the target placed at various angles. The saving in film for experimental purposes in this procedure is obvious. It is recommended that the following technic be used in making the records described: kv.p., 40; ma., 10; sec. 10. The distance of the target to the lead grid is not to exceed 4 inches; the usual film distance is set by the apparatus. Cardboard film holders are used. Enlargements may be made by increasing the distance to the film. Under no circumstances may the kilovolt peak be increased above 40, as the danger of spark-over through the lead grid is imminent. Descriptive Data 1. Westinghouse Treatment Tube, tungsten disc (Fig. 1): Dark ring— Actual focal spot. Lighter halo— Margin of focal spot. Wide halo— Outside edge of entire anode. 2. Universal Broad Focus, solid tungsten anode (Fig. 2): Dark center— A crater on surface. Light ring— Flat surface. Dappled outer dark ring— Melted raised areas on target. Outer halo— Outer margin of anode. 3. Universal Medium Focus, solid tungsten anode: good condition (Fig. 3): Dark— Actual focal spot. Halo— Anode. 4. Universal Fine Focus, solid tungsten anode: good condition (Fig. 4): Dark— Actual focal spot.

Conditions of the Halo Formation Around Subtilis Colonies and Growth of Halo Transplants

An interesting phenomenon was described which certain B. subtilis strains show when grown on nutrient agar containing a small amount of saccharose. The amorphous, stringy material which is present in abundance in the cultures as an intercellular substance spreads out from the colonies and forms a wide halo around them. In the halo bacteria are not visible and transplants of it do not grow on the usual media. Transplanted on agar plates containing saccharose the halo substance grows in tiny transparent colonies. The observations described in the following note furnish convincing evidence that these growth phenomena are caused by the growth of living elements entirely different in morphology from the usual forms of bacteria. The observations here described concern the conditions under which the halo develops and which determine the abundance of growth in the transplants. The formation of the halo depends on the addition of saccharose to the nutrient agar. Usually as small an amount as 0.02% is sufficient and about 0.1% gives the best results. It is probable that the saccharose itself is effective and not an impurity in the saccharose preparation; because, by fractionation of saccharose with alcohol, no fractions were obtained which had increased or decreased potency. Other sugars have no effect on the halo formation. The formation of the halo depends largely upon the condition of the surface of the plate. The production of the halo can be greatly improved by rubbing the surface of the agar plate lightly with a glass rod. The different batches of agar vary very slightly and the addition of different animal proteins, fresh plant tissue, cystein, etc., produced no effect. When the pH is varied between 6 and 8.5 there are no marked changes.

Curious Shadow Effect

IN connection with the “Curious Shadow Effect” mentioned by your correspondent, Mr. H. M. Warner (NATURE, January 28, p. 296), may I be permitted to direct your attention, and his, to a somewhat peculiar “species” of Brocken which I attempted to describe some years ago in the Scottish Mountaineering Club Journal (vol. ii. pp. 32–33, 1893)? I ask this, not with any idea of replying to Mr. Warner's inquiry, but to ask another question which perhaps may be answered at the same time. Referring to the above mentioned note, I ask the question, “How was it that more than one image was visible to each of our party?” “Standing close together, all five or six images were visible, all within the wide outer halo; but of course, not one of us saw more than one set of concentric rainbow bands or circles—R.O.Y.G.B.I.V.—and at the lower limbs of the halos nothing of our reflections could be seen, because we were standing slightly below the dip of the ridge.”

Telescopic Definition in a Hazy Sky

The diminution of star disks during temporary haze or even by a thin passing cloud has been particularly noticed by Sir John Herschel. The effect of this haze is apparently to diminish the intensity of diffraction phenomena. The markings on the full moon have never been seen so blackened and distinct as through the haze of a London fog. On one occasion a very gentle east wind brought down a London fog to Reading. That evening the air was extremely still, but embrowned with the haze. Castor bore a magnifying power of 600 with a Wray 51/4 acbromatic. The object-glass was being adjusted to the axis of the tube. Finally an intense jet black ring was seen to surround each star of this celebrated double, supplemented with one bright perfectly defined diffraction-ring, then a fainter ring at a further distance could be descried. The perfection of this definition has never since been attained. The haze had settled down into still air. The eastern breeze had died away. The brown fog remained in the sky; diffraction assumed its most perfect form. The moon bore any power I could muster with absolutely steady definition. These states of the atmosphere are extremely rare. I can now record a repetition of this wonderful steadiness. On November 9 Col. Abadie, Mr. Maunsel, and myself, were observing Saturn with an 81/2 Calver mirror. The crape veil and belts were well shown with the pale blue Polar cap. Ball's division was intensely black. The outer ring was narrow, and its dark grey tint contrasted strongly with the brilliant whiteness of the inner ring. I was greatly astonished, however, to descry Encke's division on the outer ring usually called A. The shadows of the ball were well marked. The eastward shadow much stronger than the western. A very brilliant narrow band edged the northern belt near the plane of the rings. The inner edge of the ring B projected a thin shadow on the ball. A lady who had no previous knowledge of the belts, entering the observatory last night, said they appeared to consist of several fine lines of parallel bands separated by very fine brighter bands. At 11 p.m. there was a very wide narrow halo round the moon. Saturn appeared much bedimmed, and Jupiter shorn of his brilliance. Yet Col. Abadie writes: “Jupiter was a sight to be remembered. The distinctness of all the belts was enhanced by bright zones; one to the north of the uppermost belt was particularly to be noticed. The clouds between the equatorial belts changed in appearance from being very fleecy to a long wavy appearance” (we were observing about three hours). The moon was too dim for observation. Encke's division is so seldom seen in my experience, its appearance in the field of so small a telescope was a matter of great surprise; and but for the concurrent testimony of two others for about a space of three hours, I certainly should have greatly doubted the accuracy of the observation. At all events, it is a valuable demonstration of the value of the chiaro-oscuro in astronomical research.