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slower masses of warmer air. At a moderate height condensation took place in the moist, upthrust air, and as it ascended at a lesser rate of cooling, due to the liberation of the latent heat of condensation, it probably was squeezed aloft at an increased rate by the cold wind it was probably encountering. Under such conditions intense vertical movement accompanied by a rotary motion of small dimensions makes a tornado.

The circumstances surrounding the formation of the tornadoes of April 20 were somewhat different. In this case, there was a long, oval-shaped low pressure area over the southern part of the Mississippi valley. The storms occurred in the morning at a time when the line of wind-convergence was a considerable distance to the west of the line of tornado formation. Therefore, it can not be said, as in the previous case, that the mechanical effect of the wind-shift line was operative. There is another striking feature: All of these whirls were formed along a north-south line which lay about 30 miles west of the Mississippi-Alabama line. The first occurred at Ingomar at 7:30 and followed a northeasterly course into Tennessee where it continued by a series of dips almost to the center of the state. The second began about 40 miles south of the first, near Bradley at 8:00 A.M. and moved northeastward, disappearing in northcentral Alabama. The third began near New Deemer, at 8:30 A.M. and ended near Brownsboro, Alabama. (This was the longest of the four paths, and was marked by an almost continuous swath of destruction for 150 miles.) The fourth appeared at Bay Springs at 9:55 and ended near the state line east of Meridian, having passed within a mile of the Weather Bureau office at that place. The significant facts are, (1) that these tornadoes formed on nearly north-south line, and (2) that they formed at almost equal intervals of time and distance. The probable explanation is that these formations resulted when an overrunning layer of cold air arrived over a given place, where other conditions were favorable, increasing the vertical temperature gradient to such a degree that there was immediate and


intense convection. That this advancing front was probably coming from the northwest is shown by joining the positions of the tornadoes at any given time. The resulting line is normal to the wind direction supposed to exist aloft.

According to Mr. J. H. Jaqua, the Weather Bureau meteorologist at Meridian, Mississippi, the passage of the tornado at that place was accompanied by almost total darkness. He


.. The darkness between 10:30 and 10:39 A.M. was as intense as would be common for a cloudy moonless night at 9:30 or later, and though lights were on in the business houses (but no street lights were in operation), pedestrians could distinguish each other only with great difficulty. . . . The pall of darkness was so unnatural that it was extremely weird.

No account of tornadoes is complete without the recital of some of the many 66 freaks" which such storms are wont to perform. The removal of feathers from chickens, the complete destruction of houses, the clean sweeping through deep forests, and the carrying of objects great distances, are examples frequently recounted. Of the many curious pranks of these storms, however, there are some which are worthy of mention. Here are some excerpts from the numerous accounts in the article cited above:

An automobile locked in a garage was undamaged, although the garage was blown to splinters.

Half a dozen glass jars of fruit were carried 100 yards by the winds and not damaged. (Bay Springs, Miss.)

A car load of stone was whipped about like a feather, and trees, one especially large oak, were twisted from the roots as if they had been bits of wire. (Florence, Ala.)

There seemed to be two puffs of wind; one carried things toward the west. In about a quarter of a minute everything came back. I tried to keep my family down on the floor. One of my boys blew out of the house; then blew back. ... (From report of J. P. Sanderson, Newburg, Ala.)

[The tornado] swept rapidly across the cove, as it neared the mountain range and went over it, leaving a path clear of any standing timber, houses, or fences. In going over the path of

the storm the next day... cedar trees, with trunks 16 inches through [were found] lying on the upper benches of the mountain, that had been torn up by the roots down in the valley and brought up bodily and deposited among the big timber on top of the range. . . . (Postmaster Okal, Huntsville, Ala.)

. . . A mule was hurled 100 feet against a tree stump, its body pierced by a 2 by 4 scantling; a horse was carried several hundred feet into a patch of wood where it was found the following morning apparently unhurt; a steel range from the Preston home was found 3 miles away in a wheatfield; harrows, plows and other agricultural implements were scattered over the fields for miles around; a sewing machine was found hanging from a tree limb. . . . (Occurred in the tornado of April 12, in Union County, N. C., according to Mr. G. S. Lindgren.)


This list could be continued indefinitely, and it is presumed that each locality visited could yield a number of remarkable "freaks."

The series of articles in the Review is concluded by a reprint from the "Physics of the Air," by Dr. W. J. Humphreys on the "Tornado and its cause," and a bibliography prepared by Professor C. F. Talman, which gives the principal publications containing statistics of tornadoes in the United States.

It is needless to say that the twenty-one or more tornadoes which have been experienced in the United States this spring, have been terribly destructive of life and property. It is estimated that in the tornadoes of March 28 killed 163, injured several hundred and destroyed ten million dollars worth of property. Those of April 20 were even more destructive of life, there being 229 deaths reported and over 700 injured, with a property loss also extending into the millions. This most destructive of storms is so extremely local that even though there may be a wind speed of between two and five hundred miles per hour in the funnel-cloud, this speed falls off so rapidly with distance from the center that the wind may not even be of destructive violence within a few hundred yards. Owing to this extreme localization, the tornado can not be accurately forecast; and if it could, it

2 Journal of the Franklin Institute, January, 1918, pp. 114-116.

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UNDER the above title an interesting note has just been published by Professor C. V. Raman and Mr. Ashutosh Dey.1 The authors call attention in a footnote to the fact "that the splash of a liquid drop is practically soundless unless the height of fall exceeds a certain minimum." In connection with this remark it seems perhaps worth while to publish a note on a preliminary study of a similar problem which I made in 1915. I have been intending to return to the work, but have been giving my attention to other matters.

My observations were confined to drops of water falling into water, and were made by ear. They indicate not only a single minimum height of fall within which the drops strike the water silently, but also other greater heights of fall for which the drops enter the water without sound. The boundary between a region in which a drop makes a sound when it strikes and a region in which it does not make a sound when it strikes is very sharp, a fraction of a millimeter difference in the height of fall being sufficient to pass from a drop which falls silently to one which makes a sharp click when it strikes.

In the figure the results of five experiments are shown. The numbers at the left give the distances in centimeters from the orifice from which the drop fell to the surface of the water below. Each vertical line indicates a range throughout which the drops click when they strike the water. The maximum heights of fall tried are indicated by the horizontal dotted lines.

It will be seen that in most cases a drop strikes silently if it falls less than about 5.5 cm., if it falls more than about 7 cm. but less

1 Phil. Mag. (6), 39, p. 145, January, 1920.

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strikes makes no difference so long as this distance is more than about a centimeter. The depth of the water surface below the top of the containing vessel appears to be without effect.

Instead of the characteristic sharp click of the drop there was occasionally a softer, duller sound, and when this soft sound occurred the drop often left a bubble at the point where it had struck. In the case of the click no bubble was usually left.

I have no explanation to suggest for this series of sounds. If they depended on the shape of the drop when it struck the water we should not expect an abrupt boundary between the regions of sounding and the regions of silence, and we should expect the series of regions to repeat at distances proportional to the squares of the successive integers.



THE CRYSTAL STRUCTURE OF ICE X-RAY photographs of ice were taken to determine its crystal structure following the method used by A. W. Hull. The lines on the film correspond to those of the hexagonal system. They show that ice has a lattice which is built up of two sets of right, triangular prisms interpenetrating one another in the following way. Consider the plane containing the bases of one of the sets of prisms. The molecules lie at the vertices of equilateral triangles of side 4.52 Ångstroms. At a distance of 3.66 Ångstroms above this plane lies the plane containing the bases of the second set of prisms. Here the molecules also lie at the vertices of equilateral triangles equal to those of the first set, but each molecule is situated directly above the center of one of the lower triangles. The other molecules of the crystal will lie directly above the molecules of the two planes just described at intervale of 7.32 Angstroms. The above values give an axial ratio of 1.62 in good agreement with the crystallographer's value of 1.617.2 From 1 Phys. Rev., 9, 85, January, 1917.

2 Gmelin Kraut, "Handbuch der Anorganischen Chemie," Heidelberg, Vol. I., 1, p. 107, 1907.

these data the number of molecules at each point has been calculated to be two.

This means that the molecule of ice must be of the form (H2O), or H,O,. The full data and calculations will be published in the Physical Review. D. M. DENNISON

August 20, 1920




W. K. Lewis, chairman

Arnold H. Smith, secretary

Discussion of report of committee on "Physical Testing."

A direct method for the determination of rubber hydrocarbon in raw and vulcanized rubber: W. K. LEWIS and W. H. MCADAMS. It has been shown by a volumetric method involving a double titration that the bromine consumption, corrected for the observed substitution is a true measure of the actual amount of pure rubber hydrocarbon known to be present. Although the amount of substitution increases with the length of the bromination period, the addition corresponds quantitatively to the actual amount of pure rubber hydrocarbon present when the bromination time is from two to four hours. Experimental data is given to show that the actual per cent. of (CH1)n in vulcanized soft rubber can be determined by a volumetric bromination method herein described, involving a second titration to correct for the substitution which accompanies the particular analysis by titrating in dim daylight, this substitution correction can be made very small.

The value of shoddy in mechanical rubber goods: J. M. BIERER. A chart was presented which gave the cost relations between scrap rubber and reclaimed rubber. The value of this reclaimed rubber was evaluated on a basis of tensile strength and compared to a corresponding priced new rubber. A line of demarkation through the center of the chart showed where it was more economical to use new rubber or reclaimed rubber.

The recovery of volatile solvents: W. K. LEWIS. Solvents used in the rubber industry may be recovered by the use of any method such as absorption, compression or cooling. Ordinarily in

the rubber industry the solvent vapor is diluted with a large quantity of air and in this case the absorption method is best. When such conditions are present so that one has concentrated vapors a Benzol compression method becomes available. used in pregnating cord tire fabric may be recovered with an efficiency of 90 per cent. by enclosing the impregnating apparatus and passing the vapors through an absorption tower. The danger of fire or explosion may be eliminated by passing flue gas into the apparatus.

On the determination of true free and true combined sulphur in vulcanizing rubber: W. J. KELLY. At present sulphur is considered as free and combined. Acetone soluble sulphur may be partly combined with resins, etc., as may also the sulphur insoluble in acetone, heretofore considered as combined with rubber. The total acetone extract is soluble in EtOH, but if EtOH saturated with sulphur is employed, none of the truly free sulphur will dissolve and hence can be separated from the remainder of the extract. Results show about 0.4 per cent. sulphur combined with resins, etc. About 85 per cent. of Heva resins are saponifiable and hence any resinous sulphur compounds insoluble in acetone may be soluble in alc. KOH. Acetone extracted sample is boiled 8 hours in 5 per cent. alc. KOH and about 0.26-0.30 per cent. sulphur extracted. Successive extractions do not increase this. Hence, the rubber is not being decomposed. These results are on pure gum and sulphur stocks and will be extended to compounded stocks later.

Analytical determination of the coefficient of vulcanization: S. W. EPSTEIN.

Small amounts of magnesia and certain organic substances as accelerators: G. D. KRATZ and A. H. FLOWER. The activity of small amounts of extra light magnesia as an accelerator was compared with the effect of similar amounts of certain organic accelerators. The load required to effect a given extension was found to be a fair measure of the rate of cure of the mixture which contained magnesia; however, this was not true for the mixtures which contained the organic accelerators. The accelerating activity of magnesia in small amount was found to be of secondary or contributory, character, acting in conjunction with, or in response to, certain extraneous substances, probably nitrogeneous, present in the rubber. The amount and nature of these extraneous substances was found to limit the activity of magnesia as an accelerator.

Diffusing power of pigments: W. K. LEWIS and F. P. BAKER. The diffusing power of pigments can be determined by measuring the weight of pigment per unit of cross sectional area necessary to obscure objects behind a suspension of the pigment, the result being expressed as square centimeters per gram or square feet per pound. The determination can be carried out in simple apparatus and results can be checked with accuracy. It is believed that the diffusing power is the most satisfactory measure of the fineness of a pigment, and as such is of obvious interest and value to the rubber trade.

The effect of compounding ingredients on the physical properties of rubber: C. OLIN NORTH. Compounding experiments in which from one to fifty volumes of filler, i. e., gas, black, zinc oxide, etc., were added to 100 volumes of rubber are described. The values obtained for tensile strength, etc., are corrected back to the actual volume of rubber present and another set of curves drawn. Tensile strength calculated on area at rest is unfair to a soft stretching stock. Tensile at break is suggested as a better basis of comparison. This is obtained by multiplying usual tensile strength by final length and dividing by the original length times a correction factor, because of volume increase during a stretching. A visual picture of the physical structure of rubber, i. e., network hypothesis based on the assumption that large colloidal aggregates function as elastic fibres and the smaller as plastic material is presented. Vulcanization probably locks up these fibers to form a network.

The microscopic examination of rubber and rubber products: HENRY J. MASSON and IRENE C. DINER. The authors presented the results of their investigation in the line mentioned in the title. Magnifications of from 500 to 2,000 diameters were used. Best results were obtained at magnifications of about 800 diameters. The ordinary methods of metallurgy were resorted to, both oblique illumination and vertical illumination being used. Photomicrographs were shown at the meeting of various samples which had been examined.

Rubber chemistry from the colloidal viewpoint: ELLWOOD B. SPEAR. The mechanism of crystallization, condensation, polymerization and coagulation was discussed. Gelation is one type of coagulation. Selective adsorption is given as a reason for the increased tensile strength of compound rubber. This deals with the different surface

energy of rubber and the various compounding ingredients.


Louis E. Levi, chairman
William Klaber, secretary

The true tanning value of vegetable tanning materials: JOHN ARTHUR WILSON and ERWIN J KERN. A new method of tannin analysis is described which determines exactly what is called for in the generally accepted practical definition of tannin, namely, that portion of the water-soluble matter of certain vegetable materials which will precipitate gelatin from solution and which will form compounds with hide fiber which are resistant to washing. The analyses of 10 common tanning materials by the new method and by the official method of the American Leather Chemists' Association indicate that the latter method is in error to the extent of from 43 to 220 per cent. The new method gives reproducible results and is considered entirely practicable.

The neutral salt effect and its bearing upon leather manufacture: JOHN ARTHUR WILSON and EDWIN A. GALLUN. The addition of neutral salts to the various liquors used in making leather is shown to have the effect of increasing the activity of all the constituents of such liquors, whether they be acid or alkaline. In the case of chloride salts, this was shown quantitatively to be due to removal of solvent by hydration of the added salt. The results of 37 experiments in chrome tanning with different kinds and proportions of neutral salts are given which throw considerable light upon the mechanism of chrome tanning.

The determination of sulfate in sulfonated oils: ERWIN J. KERN. In the determination of uncombined sulfate in sulfonated oils, the use of organic solvents can be dispensed with, if the usual brine solution be replaced by a 10 per cent. solution of monosodium phosphate, which gives a clear separation of solution and oil in very few minutes. After boiling the oil with hydrochloric acid, total sulfate may be determined in the same way. The phosphate solution extracts all of the sulfate in each case, which may then be determined as barium sulfate in the usual manner. A saving of time is effected by the new method.

A new method for the determination of sulfuric acid in leather: ARTHUR W. THOMAS.

Time factor in the adsorption of the constituents of chromi sulfate solutions by hide substance: ARTHUR W. THOMAS and M. J. KELLY.

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