Jan. 9, 1890J 



NATURE 



237 



critical point of the whole reasoning is whether the observed 

 temperatures at the three stations Roorkee,Dehra, and Mussooree, 

 can be safely accepted as approximately representing those of the 

 free atmosphere over the plains at the same levels, and this 

 seems to us at least open to question. In the case of the lowest 

 and highest stations, indeed, there is not much to object to. 

 Roorkee is a fairly representative station of the northern part of 

 the Gangetic plain, and the Mussooree Observatory, situated on 

 the very crest of the ridge of the Himalaya, overlooking the 

 plains, is probably as little affected by the local heating of the 

 ground as any mountain observatory can be. But Dehra, which 

 furnishes the really critical datum of Mr. Hill's reasoning, is on 

 the plain of the Di'in, a flat valley six or eight miles across, 

 stretching between the Sivaliks and the foot of the Mussooree 

 ridge, and it is by no means self-evident that the local tempera- 

 ture is not largely affected by causes which are quite inoperative 

 in the free atmosphere at the same elevation over the plains. 



In our opinion, then, Mr. Hill's conclusion that the storms of 

 April 30 and May i were determined by a change in the vertical 

 distribution of temperature, transferring the condition of in- 

 stability from the lower to the higher atmospheric strata, is at 

 least open to doubt. To a certain extent, indeed, it is supported 

 bytheevidence of other observatories in the North-West Himalaya, 

 especially Chakrata, the situation of which is very similar to 

 that of Mussooree; but the difference of their elevation (170 

 feet) is too small to allow of its having much weight in determin- 

 ing the point at issue. 



The most noteworthy feature of the storm of April 30 was the 

 fearful loss of life caused by it at Moradabad. Not less than 230 

 deaths were reported at this station alone, the vast majority of 

 which were caused directly by the hail. The collector's report 

 states that men caught in the open and without shelter were 

 simply pounded to death. The spring is especially the season of 

 native weddings, and "more than one marriage party was 

 caught by the storm near the banks of the river and was anni- 

 hilated." It is, however, suggested by Mr. Hill that many of the 

 deaths may have been caused by cold. "Immediately before 

 the storm the temperature had been very high, and many if not 

 the majority of the deaths due to it may have been occasioned by 

 the persons exposed to its fury being knocked down and temporarily 

 packed in ice." At Moradabad the hailstones are stated to have 

 been the size of plums — probably the ber plum, Zizyphus jujtiba, 

 the cultivated form of which is two or three times as large as a 

 walnut. 



In the storm of May i, the hailstones at some places were 

 larger, though the destruction was less. At Ghaziabad they are 

 said to have been as large as cricket balls, and one was picked 

 up at Delhi weighing 4? ounces. At Tilhar they are reported 

 to have been larger than goose eggs, and at a neighbouring 

 place they averaged 3 inches in diameter. Their form is 

 described as a flat oval. 



SCIENTIFIC SERIALS. 



BtiUdin de f Academic Royale de Belgique, November 1889. — 

 On the existence of a gizzard, and on its structure, in the family 

 of the Scolopendridse, by M, Victor Willem. The presence of 

 a gizzard in the lower organisms was first determined by M. F. 

 Plateau in 1876. But the gizzard of insects was long supposed 

 to be merely a triturating organ acting mechanically, without 

 any physiological function. Continuing Plateau's researches, M. 

 Willem now finds that the gizzard is not only present in several 

 genera of the Scolopendrid family, but that it is a true digester. 

 The structure is fully described, and illustrated by two plates, 

 on which are figured the gizzards of Scolopendra hispanica, S. 

 cingulata, S. heros, Scolopocryptops, Cryptops pnnctatus, and C. 

 hortensis. In these last, the apparatus is most highly developed, 

 being even more complicated than amongst the higher order of 

 insects. No explanation is offered of this apparent anomaly. — 

 Unexpected proof of diurnal nutation, and necessity of taking 

 it into consideration in the reduction of observations, by M. F. 

 Folie. The coefficient of diurnal nutation as already approxim- 

 ately determined at o-ois. by the author's numerous researches, 

 has recently been confirmed in a somewhat remarkable manner 

 by the results of M. Kobold's observations of the Polar star 

 with the meridian circle of Strassburg. The azimuthal errors 

 of this instrument were found to present, not an annual, but a 

 diurnal period, and Kobold's corrections are shown to be 



illusory, being due to his neglect of the element of diurnat 

 nutation in the reduction of his observations. When this ele- 

 ment is taken into account, the results harmonize with those 

 previously arrived at by M. P"olie. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, Dec. 19, 1889. — " On the Effects of Pressure 

 on the Magnetization of Cobalt." By C. Chree, M.A., Fellow 

 of King's College, Cambridge. Communicated by Prof. J. J. 

 Thomson, F.R. S. 



It has long been known, from the classic researches of Dr. 

 Joule, that a rod of iron free from stress increases in length whea 

 magnetized in a comparatively weak field. When, however, the 

 strength of the field is contmually raised, it has been found by 

 Mr. Shelford Bidwell that the rod ceases to increase in lengthy 

 and then shortens, so that in a sufficiently strong field the length, 

 becomes less than it was originally. It has also been found by 

 Villari, Sir W. Thomson, and others, that when a rod of iron is. 

 exposed to successive loadings and unloadings of a given weight 

 in a magnetic field, there appears a corresponding cyclic change 

 of magnetization. In this cyclic change the maximum mag- 

 netization occurs when the load is "on," or when the load is 

 "off," according as the field is weaker or stronger than a certain 

 critical field depending on the load, called by Sir W. Thomson, 

 the Villari crhical field. 



Cobalt has been found by Mr. Shelford Bidwell to shorten- 

 when magnetized in weak fields, but to lengthen in very strong 

 fields. The field in which it ceases to shorten is very much 

 higher than the field in which iron ceases to lengthen. Also in 

 weak fields Sir W. Thomson has found the magnetization of a 

 cobalt rod under cyclic applications of tension to be least when 

 the tension is " on" 



Now, Prof. J. J. Thomson has shown that on dynamical 

 principles the effect of changes of magnetization on the length 

 of a rod of magnetic metal, and the effect of changes in the 

 length of the rod on the magnetization, must be fundamentally 

 connected. In his "Applications of Dynamics to Physics and 

 Chemistry," he has arrived at mathematical equations connecting 

 the two phenomena, such that from a knowledge of the one set 

 of phenomena the character of the other set can be deduced. 



The conclusions derived from the theory are in the case of 

 iron in accordance with the results of experiment, at least in 

 their general character. In cobalt there is also an agreement 

 between theory and experiment, so far as Sir W. Thomson's 

 experiments go. In the absence of further experiments it 

 would, however, be impossible to tell whether or not this 

 agreement extended to the strong fields in which occurred the 

 important phenomena observed by Mr. Shelford Bidwell. The 

 application of Prof. J. J. Thomson's formulae to Mr. Shelford 

 Bidwell's results led him to the conclusion that under cyclic 

 applications of pressure a cobalt rod should experience cyclic 

 change of magnetization, and that the maximum magnetization 

 should answer to pressure " on," or to pressure " off," according 

 as the magnetic field was weaker "br stronger than a critical field, 

 corresponding to the Villari field in iron. It was for the purpose 

 of determining whether such a critical field did actually exist 

 that the present investigation was commenced at Prof. J. J. 

 Thomson's suggestion. 



Employing the magnetometric method, it was found that the 

 agreement between theory and experiment was at least as satis- 

 factory in cobalt as in iron. The application of pressure-cycles 

 in a magnetic field led to a cyclic change of magnetization in a 

 cobalt rod, in which the maximum magnetization occurred when 

 pressure was "on," or when it was "off," according as the 

 strength of the field was below or above 120 C.G. S. units. 

 This accordingly was the Villari critical field foreshadowed by 

 theory. 



In weak fields the first pressure applied after the introduction 

 of the cobalt rod into the magnetizing coil caused a large in- 

 crease in the induced magnetization. As the strength of the 

 field was raised, this change in the magnetization attained a 

 maximum, then, diminishing, vanished in a field considerably 

 stronger than the Villari field for the cyclic effect, and in all 

 stronger fields consisted in a diminution of magnetization. 



Both Villari and Prof. Ewing observed that, after the break 

 of the magnetizing current, cyclic changes of tension produced 



