expressing the proportion between the resistance to pressure in a dry and in a wet state. In addition to the above, Hempel's test with muriatic acid deserves mention. lation from the outer air, the former being more effectual, but the latter preferable on account of its cheapness. In the selection of the stones, as well as in the general conduct of the experiIn reviewing these processes, Herr A. ments, Herr Blümcke had the advantage Blümcke points out in the Thonindustrie of the advice of Professor Gottgetreu, Zeitung that all of them subject the ma- the trials being conducted in the laboraterial to conditions which are not to be tory of Professor Von Beetz. The stones found in practice, while their more or were in cube form, the length of the sides less complicated nature forms an obstacle being about 3 inches, and the surfaces to their adoption. On the other hand. roughly dressed. Two specimens were the process of Bauschinger is more prac- tested in each case, and one of them was tical, consisting in the exposure of the completely saturated with distilled water. material twenty-five times to frost in the Boiling was, however, avoided, so as not open air, the strength before and after to expose the material to a degree of the test serving as a guide to the resist heat which it is not in practice called to ing power. The production, by artificial endure. When a material is very porous means, of the needful degree of cold it is impossible to freeze it when thorsuggests itself, but hitherto this process oughly saturated. After removal from has only been accomplished by the aid of the refrigerating apparatus the cubes chemicals, which affect the substances were placed in a small trough, covered treated in such a way as to prevent the with water, and left there three hours, ready appreciation of the effects produced so as to again be brought to the temperby frost. Hence, a proposal of Hericat ature of the room. When taken out the de Thury has been carefully studied by stones were covered with a coating of Herr Blümcke, with the result of his per- hoar frost, and if then left for some time fecting the following method: in water a loosening of small particles was perceptible in the portions not capable of resisting frost. Before the next subjection of the stones to the refrigerating process the surfaces were gently rubbed with a feather. Herr Blümcke repeated the process until distinct traces of injury were visible, such as cracks, peeling, loosening of corners, &c. If a stone had been ten times subjected to the frost, with such traces appearing, the quantity of the mass separated after the evaporation of the water was ascertained, and the process continued until destruction commenced. A second cube was subjected to a stream of water during one hour upon three sides. In this case there was no attempt made to ascertain the loss of volume, but the application of the water was continued until injury became apparent. These external appearances were quite the same as if the stone had been saturated, but were considerably later in manifesting themselves. The stones to be tested are placed, two at a time, in a wire framework suspended from a rod. These are placed in a cylindrical metal vessel, sloped off at the foot in funnel form, and with a cover. This is inclosed in a larger vessel of the same shape, and held in position by supports. There is a space of 2 inches around the smaller vessel, which space is filled with a refrigerating mixture. A vessel, 2 inches in height, is also placed above, filled with the same mixture. At one time an escape-pipe had been in use at the lower part of the apparatus, but it was found more practicable to empty it after each operation by a siphon. The cold mixture used consists of three parts of ice in small pieces and one part of powdered rock salt, its cheapness being a considerable advantage. The lowest temperature obtained in the interior of the apparatus was below 10° Fahrenheit, although a still lower temperature could have been arrived at. Small thermome- From these experiments Herr Blümcke ters were inserted in the stones, and although two hours sufficed to bring these to the temperature of the surrounding air, the stones were subjected to the process during a period of three hours. Felt or sawdust was used to procure iso has deduced the theory that a material has higher properties of resistance to frost, according to the restriction of the loss in weight, caused by the repeated application of the freezing process. In trials made upon sandstone the following results were obtained. In all cases cracks edges), and produced crumbling when were finally visible which ran close to the operations were persevered with. each other (parallel to one or several Large pieces were detached from No. tions during an average winter between 1, and cracks appeared all over Nos. 2 frost and thaw. When thoroughly satuand 3. On No. 4 there were two kinds rated stones are tested, the results are of coatings, a darker one, which broke off applicable to the most unfavorable cirmore than the other, and a lighter one, cumstances, and are consequently the which showed cracks. Nos. 6 and 8 more reliable. Should a material not peeled on the surface, and No. 7 was show injury at the temperature applied, much cracked. After the thirteenth this fact does not establish its power of freezing of the ninth type a splinter be- resisting frost, but renders advisable the came detached from one corner, but trial of a still lower temperature; in no cracks parallel to the edge were not visi- case, however, below the range to which, ble till after the forty-third freezing. in practice, the stone would be subjected. Finally, Herr Blümcke does not claim that he has solved all the questions connected with this interesting subject, but considers that his illustration of what may be done with simple means, by skillful and capable hands, may not be devoid. of value to the cause of science. By proceeding in this way it is not necessary to wait for the visible destruction of the material. Coupled with the definition of the degree of resistance to frost is an approximate estimate of the period a stone will last, as it is not difficult to arrive at the number of alterna COMPARATIVE EXPERIMENTS ON THE WELDING OF STEEL AND WROUGHT IRON. BY J. BAUSCHINGER. THESE experiments were undertaken by (Flusseisen). The author recapitulates the author at the instance of an engi- the main results of these tests before neering firm. Similar experiments had been previously made at the Royal MechanicalTechnical Experimental Institute at Berlin, and by Mr. W. Hupfeld, at Prevali, which gave very different results; those at Berlin being very unfavorable, those at Prevali very favorable, as regards the welding capacity of steel describing those made by himself. The materials used in the latter were steel (Flusseisen), from the "Peine" ironworks at Hanover, and bar iron of various sections from the "Neuhoffnungshuette," near Herbauer, in Nassau. The test-pieces were flat, square, and round in section, the largest being 80× 30 millimeters (3.149 × 1.181 inch). Each piece was cut in two cold, swelled up on form. Both for steel and iron the limit the anvil when hot 5 to 10 millimeters of elasticity is nearly always reduced by (0.196 to 0.392 inch), and, after heating welding, and this is, without exception, to the proper degree, the two portions the case as regards the extension, the were laid on each other, and welded to- contraction of welded is less than that gether by hand or steam hammer. of unwelded pieces when the fracture takes place in the welded portion. Some preliminary studies were made in the laboratory of the college to ascertain the best method of welding, and the best flux for steel; quartz sand answered the latter purpose, while it was found that a rather less degree of heat was required for steel than for wrought iron; a pure coal fire was used. The general conclusions arrived at are, that for steel the best welding temperature is just at the transition from a red to a white heat; a quick fire and smart handling are necessary, as the piece should not be long in the fire. Analyses were made of three samples, one of which welded admirably, the second badly, and the third not at all. In the chief experiments the steam hammer was employed. Every piece, after welding, was tested in the usual The author is of opinion that, in the case way for tensile strength; the limit of of mild steels, such as those tested, elasticity, contraction, extension, and ul- with a low carbon, intended to take the timate strength being determined, the place of bar iron, success, or otherwise, same quantities having been measured in welding, depends less on the chemifor pieces of exactly similar quality, sec- cal composition than on the mechanical tion, and length, but without a weld. treatment.-Abstract of Inst. of Civil The results are given in a tabular Engineers. IMPROVEMENTS IN THE ARRANGEMENT AND RATING OF CURRENT-METERS, AND IN THE METHOD OF CALCULATING DISCHARGES. BY CHARLES RITTER. From "Annales des Ponts et Chaussées," for Institution of Civil Engineers. A DETAILED account is given by the for gauging has slipped by during the author of the elaborate investigations preliminary operations. which he conducted, with the object of The gauge-tube adopted has the pressrendering more serviceable the two gaug- ure-gauge distinct from the nozzles, ing instrument generally employed in which are connected together by indiaFrance, namely, Darcy's gauge-tube, and rubber tubes. The rod carrying the nozWoltmann's current-meter as improved zles is thereby made much more handy, by Mr. Baumgarten; for the purpose of whilst the observer can suspend the facilitating the rating of these instru- pressure-gauge so as to keep the summits ments; and lastly, for improving the of the two columns of water always in methods of calculating the discharge view, whose oscillations are considerably from the indications furnished by the instruments. The ordinary type of gauge-tube is awkward to handle; and gauging with a current-meter which has to be drawn up out of the water for each reading is a slow process, especially at great depths. Moreover, the rating of these instruments has hitherto been frequently so difficult, slow, and costly, that either the rating has been dispensed with, thus introducing an uncertainty in the results, or the most favorable time reduced by means of a regulator interposed between each india-rubber tube and the gauge. The nozzle pointing towards the stream has not been altered in type, but its best form consists of a straight tube 0.2 inch in diameter, and 4 to 6 inches long, tapered at the extremity, and presenting a cylindrical orifice of 0.08 inch in diameter throughout the tapered portion. The side nozzle, however, has been replaced by a statical mouthpiece, which indicates the pressure This type of instrument is not suitable for considerable depths, both on account of the difficulty of handling an apparatus of over 10 feet in length when raised out of water, and also owing to the escape of air-bubbles when the pressure is reduced in the tubes by immersion, necessitating constant readjustments. These difficulties, however, might be obviated by using a different gauge tube for each separate group of depths comprised within intervals of 5 feet. The corresponding to the surface-level of the current without needing any correction. The mouthpiece adopted for this purpose consists of a tube, 4 inches long and 0.4 inch in diameter, open at both ends, and having a lateral orifice in the middle, from 0.04 to 0.08 inch in diameter, round which the second connecting-tube is soldered. Each connecting-tube consists of two portions, one portion, a rigid copper tube, and the other, a flexible indiarubber tube. The copper tubes carry the nozzles at their lower extremities, and have The current-meter adopted has four an air-chamber at their upper ends, with spiral vanes, and is provided with an a stop-cock at the top. Each air-chamber electrical recorder for every fifty revolucommunicates with one of the india-rub- tions. It is inclosed within a hollow ber tubes by a lateral opening. The air- copper cylinder, 8 inches long, open at chambers receive the bubbles of air, both ends, having a diameter of about 4 either introduced by accidents in the inches, just large enough not to interfere manipulation or contained in the water with the revolution of the vanes. itself. The stop-cocks serve for adjusting cylinder protects the current-meter from the instrument. The copper tubes should the disturbing influences of oblique curnot be less than about inch diameter, to rents, and it facilitates the free suspenallow of the ready passage of air-bubbles sion of the instrument which is directed into the air-chambers. The india-rubber in the line of the current by a large flat tubes are made about inch internal di- plate behind. The instrument is susameter, for though they are little liable to pended in small depths, or near the surreceive air-bubbles, a very small diameter face by a hollow copper rod; but in greatwould impede the establishment of an er depths, when the length of rod necesequilibrium in the pressure-gauge. Their sary would be inconvenient, it is hung external diameter is made 0.4 inch, so from a cord formed of two insulated copthat they may be bent without collapsing, per wires, which convey the electrical which would impede the flow. The two current. The current-meter is kept in connecting-tubes are enclosed in a hollow position by a second cord (kept tight by rod, 1 inch in diameter, which is provided a weight at the bottom of the river, and with a vane at the bottom to facilitate a winch above) down which it descends, the adjustment of the line of the nozzles. being guided by rollers. The rating, beThe pressure gauge is furnished with a sides being conducted in the usual manthird tube to facilitate certain operations ner by drawing the meter through still of rating. By the adoption of the stati- water, was effected, for small velocities, cal mouthpiece, no rating is required, for by forming a very regular artificial curthe difference in the height of the two rent; and it was also obtained in the columns of water in the pressure-gauge river itself, during the experiments, by V2 placing the front nozzle of a gauge-tube without any h, is equal to coefficient 2g' in front of the axis of the current-meter being required in the equation. Also and comparing the results of the two the coefficient of gauge tubes with any methods. When the velocity of a current other side mouthpieces can be easily de- is very small, the eddies produce almost termined by connecting the mouthpiece as much effect as the direct current, so with the third tube of the pressure-gauge and observing the heights of the three columns of water in different points of the stream. The most convenient instrument of the type described has a total length of 6 feet, and is not suitable for depths exceeding 34 feet; but by screwing on a lengthening piece to the rod it can be used for depths of 5 to 6 feet. that the action of the vanes of the meter Owing to the variations and irregularities in the current, the velocities given by the instruments are always greater than the direct motion of the stream. Sometimes, also, under exceptional cir- can be obtained by tracing the lines of cumstances, the recorded velocities are equal velocity, as gathered from the obtoo low. Accordingly, in order to make servations, and prolonging these lines, in allowance for these discrepancies between accordance with the indications furnished the real and calculated results, the mean by the adjacent lines, to those parts of of two-thirds of the largest velocities, the section which cannot be reached by and the mean of two-thirds of the least the instruments. The article concludes velocities are taken, and half the sum of with some practical applications of the these two means is accepted as the actual above methods of gauging, in illustration mean velocity in the section. The mean of the processes adopted and the degree velocities throughout the whole section of accuracy attained. THE LUMINIFEROUS ETHER. BY DE VOLSON WOOD, C. E., M. A. From the Philosophical Magazine." * Two properties of the luminiferous as well as the most reliable, determinaæther appear to be known and measura- tion is by Professor S. P. Langley, who ble with a high degree of accuracy. One brought to his service the most refined is its ability to transmit light at the rate apparatus yet used for this purpose, and of 186,300 miles per second, and the secured his data under favorable condiother its ability to transmit from the sun tions; from which the value is found to to the earth a definite amount of heat be 2.8± calories* with some uncertainty energy. still remaining in regard to the first figure of the decimal. We will consider it as exactly 2.8 in this analysis, according to which, there being 7,000 grains in a pound and 15.432 grains in a gramme, we have for the equivalent energy In regard to the latter, Herschel found, from a series of experiments, that the direct heat of the sun, received on a body at the earth capable of absorbing and retaining it, is competent to melt an inch in thickness of ice every two hours and thirteen minutes. This is equivalent to nearly 71 foot-pounds of energy per second. In 1838 M. Pouillet found that the heat energy transmitted from the sun to the earth would, if none were absorbed by our atmosphere, raise 1.76 grammes of water 1° C. in one minute on each square centimeter of the earth normally exposed to the rays of the sun.† This is equivalent to 83.5 foot pounds of energy per second, and is the value used by Sir William Thomson in determining the probable density of the æther. Later determinations of the value of the solar constant by MM. Soret, Crova, and Violle have made it as high as 2.2 to 2.5 calories. But the most recent, * Professor Michelson found the velocity of light to be 289,740 meters per second in air, and 299,828 meters in a vacuum, giving an index of refraction of 1,000,265. Journal of Arts and Science," 1879, vol. xviii., p. 66 390. + Comptes Rendus, 1888, tom. vii. pp. 24-26. |