June 14, 1894J 



NA TURE 



155 



articles by members of the Italian Meteorological Society and 

 others on various subjects of scientific interest. The number 

 for May contains a note by Prof. G. Buti on Dr. von Bezold's 

 thermodynamics of the atmosphere, and attention is drawn to 

 two phenomena which up to the present time have been but 

 little studied, viz. the supersaturation and the over-cooling of 

 the air in relation to the formation of thunderstorms and varia- 

 tions of barometric pressure ; also a note, by Prof. L. Descroix, 

 on the diurnal oscillations of the barometer at Paris, based on 

 twenty years' observations. Prof. Descroix is of opinion that 

 the differences in the variations of the maxima and minima 

 from day to night, in passing from the warm to the cold season, 

 are explained by the changes of conditions of dryness in the 

 lower strata of the atmosphere, in so far as it is due to their 

 expansion and contraction. 



Thoijgh the destruction of books by insects is not so great 

 here as in India, it is sufficient to give general interest in the 

 result of an inquiry into the means of preservation adopted in 

 Indian museums {Indian Mmeiini Notes, vol. iii. No. 3). In 

 the library of the Revenue and Agricultural Department of the 

 Government of India the books are disinfected by pouring a few 

 teaspoonfuls of refined mineral naphtha, or what is knoAm as 

 benzine collas, into the crevices of the binding, and then 

 shutting up the volume for a few days in a close-fitting box to 

 prevent the escape of the fumes. Books so treated have to be 

 afterwards sponged over lightly with a very little of the finest 

 kerosine oil, which should be rubbed off with a cloth before it 

 has time to penetrate into the binding. Dr. George King reports 

 very favourably upon a system adopted for preserving books in 

 the Royal Botanical Gardens, Sibpore. It consists in brushing 

 the books over with a saturated solution of corrosive sublimate 

 made by constantly keeping a few lumps of the poison at the 

 bottom of a jar of alcohol, so that the maximum amount may 

 be absorbed. In the Indian Museum Library the books are 

 kept in close-fitting glass cases with a few ounces of naphthaline 

 upon each shelf, with the result that little or no damage is caused 

 by insects. It appears that the paste used in binding the Indian 

 Museum books is poisoned by adding about half an ounce of 

 sulphate of copper to each pound of paste, while books already 

 infested are disinfected by shutting them up for four or five days 

 in a close-fitting box of loose naphthaline with as much of this 

 substance as possible between the leaves. 



Another new method for determining the pitches of high 

 tuning-forks is described by Herr F. Melde in the current 

 number of Wiedemann's Annalen. It is. like the vibroscopic 

 method previously described, independent of the ear, and is 

 based upon the resonance of a rod clamped at one end and 

 vibrating transversely. The laws of vibration of such clamped 

 rods have already been so carefully studied that calculations of 

 pitch, based upon their dimensions and the properties of the 

 material of which they are made, are very reliable. The rods 

 used consisted of hard brass, cast steel, or iron. They were 

 32 cm. long, I cm. broad, and I 5 or 2 mm. thick. They were 

 firmly clamped in an iron clamp let into a piece of sandstone, 

 care being taken that the jaws of the clamp were strictly in the 

 same plane at right angles to the length of the rod. The 

 tuning-fork tested was mounted in a wooden block, and placed 

 with one prong lightly touching the end of the rod, so that a 

 vibration of the tuning-fork when bowed produced a transverse 

 vibration of the rod. Fine sand was dusted on to the rod. If 

 on bowing the tuning-fork the sand did not arrange itself in 

 straight lines at right angles to the length of the rod, the clamp 

 was shifted until it did. The mode of vibration, and con- 

 sequently the pitch, was then calculated from the number of 

 such nodal lines produced. An interesting application of the 

 method was the testing of .\ppunn's tuning-fork apparatus for 

 NO. I2S5, VOL. 50] 



the determination of the upper limit of audibility. One fork 

 marked 16,384, as determined by the method of beats, gave 

 really only 11,717 vibrations per second. On the other hand, 

 a standard fork by Dr. Kunig, of Paris, of pitch 16,383, was 

 found to give 16,480 by the new method — a good testimony to 

 the accuracy of both determinations. In each case, the results 

 were confirmed by the vibroscopic method. 



The current number of L' Ekttricisia (Rome) contains an 

 interesting description, by Signor Riccardo Arno, of a new ex- 

 periment he has performed. As is well known, Prof. Crookes 

 has shown that when an electric discharge is passed through an 

 exhausted tube, and a small windmill is suitably placed in the 

 path of the discharge, a continuous rotation is obtained. This 

 phenomenon suggested to the author to try if he could obtain a 

 similar rotation by placing an exhausted bulb containing a small 

 windmill in a rotating electrostatic field. The rotating electro- 

 static field was obtained by connecting four upright brass plates 

 to fixed points in the secondary of a large Ruhmkorff coil, 

 through the primary of which an alternating current was passed. 

 In order to try the experiment it was impossible to use an 

 ordinary radiometer with mica vanes, since the author in a 

 previous series of experiments had shown that when a dialectric 

 is placed in a rotating electrostatic field it experiences a force 

 tending to rotate it, in the same sense as the direction of rotation 

 of the field. Hence the author had a special radiometer con- 

 structed with thin brass vanes, since it was only by using a 

 windmill made entirely of a metal that he could be sure he had 

 entirely eliminated the direct action of the rotating field on the 

 vanes, and be sure the effect observed was due to the gas remain- 

 ing in the tube. When the electrostatic field was sufficiently 

 strong, and the surface of the glass vessel containing the vanes 

 well dried, a rotation was obtained in the same direction Jis that 

 of the field. In order to show that the rotation is not due to 

 direct action on the vanes, the author suspended a similar set of 

 brass vanes, by means of a long silk fibre, in air at the ordinary 

 pressure in the same rotating field, and found that no rotation 

 was produced. When the radiometer is under the influence of 

 the rotating electrostatic field the bulb is uniformly lighted up, 

 so that the number of turns of the vanes could be counted in the 

 dark. The author considers the effect must be due to some 

 action of the rotating field on the molecules of the gas, which 

 tends to increase their velocity in the direction of rotation of the 

 field, and thus in the case when the gas is much rarefied, so that 

 the free path of the molecules is relatively long, the impact 

 of the molecules on the metallic vanes cause the latter to rotate 

 in the same sense as the field. 



The current number of the Annali dell Islituto d' I^iene di 

 Roma contains a paper by Dr. Palermo, on the action of sun- 

 shine on the virulence of the cholera bacillus suspended in broth 

 and water respectively. The pathogenic property of all the 

 infected solutions was in each case determined by inoculation 

 into guinea-pigs, so that the difference in the toxic character of 

 the contents of the insolated and darkened tubes could be com- 

 pared with that possessed by the caolera-infected broth or 

 water solutions treated in the ordinary manner. In order to 

 ascertain what was the effect of sunshine on the number of 

 cholera bacilli present, agar dish cultures were made of the 

 insolated and darkened tubes respectively ; in no single instance, 

 however, could any numerical difference be detected in either 

 set of experiments. That the sunshine had modified the bio- 

 logical character of the bacilli, was shown very strikingly in 

 drop-cultures, for when examined from insolated broth tubes 

 they were found to have been deprived of all power of motilKy, 

 whilst the characteristic activity was still apparent in such 

 cultures prepared from the darkened tubes. As regards the 

 degree of virulence possessed by the broth cultures, those ex- 



