October 15, 1908J 



NATURE 



611 



30 days per year, but under such conditions that the amount 

 due to these 30 days is only about 6 to 10 inches, whereas 

 the annual variation of total rainfall is often 60 inches. 

 Before the forests were cut rain fell on many calm after- 

 noons, because the presence of moisture transpired by the 

 trees was sufficient by increasing the humidity and de- 

 creasing the pressure to cause slight showers. ITie rain 

 caused in this way is, however, very local, and apparently 

 Mr. Walter does not recommend any great work and expense 

 in planting trees with the idea of improving the climate 

 generally. 



The exact knowledge of the speed at which the clouds 

 travel is one of the best means of ascertaining the presence, 

 direction, and velocity of certain currents of the upper 

 atmosphere which directly affect aerial navigation. The 

 accompanying illustration shows an instrument designed for 

 this purpose, and manufactured by Richard, of Paris. 

 The apparatus is mounted on a horizontal axis around 

 which it may«be turned by means of a long screw. The 

 two supports on which it rests are fixed over a divided 

 brass disc, which may be turned horizontally around an 

 axis placed on a support fitted with three adjustable screws. 



Inside the apparatus are two mirrors placed relatively at 

 an angle of 45° in the direction of a spy-hole, through which 

 the operator looks, and towards a reticle consisting of a 

 four-sided piece of glass placed in such a way that the 

 distance between two lines represents the angular space 

 of a degree. The reticle is placed in a tube holding a 

 special system of lenses arranged in such a way that the 

 face of the reticle is reflected in the mirror. It thus 

 happens that on looking through the spy-hole the face of 

 the reticle is seen .projected upon the cloud under observa- 

 tion. It is necessary to observe the movement of iht- 

 cloud and to know its altitude in order to determine the 

 speed at which it is travelling. Two such instrumenis 

 placed at a known distance apart and observing the same 

 cloud would give the height, and, at the same time, two 

 measurements of the velocity. The mounting of the appara- 

 tus on two axes, one vertical and the other horizontal, 

 allows it to be placed at any angle, so that the sky mav 

 be explored in every direction. 



The August Bulletin of the Bureau of Standards at 

 Washington contains a paper of 132 pages on the various 

 formula; for the calculation of the self and mutual in- 

 ductances of coils, by Messrs. E. B. Rosa and L. Cohen. 



NO. 2033, VOL. 78] 



The authors have included all the formula; which have 

 been found correct, and indicate the conditions under which 

 one or other is to be preferred. The numerical work is 

 carried out in a number of cases in order to show the 

 application of the formulae, and more than twenty pages 

 of tables to facilitate the calculations are given. 



.According to a communication made to the Versamm- 

 lung deutscher Naturforscher und Acrzte at the recent 

 meeting at Cologne, Prof. H. W. Schmidt and Dr. P. 

 Cermak, of Giessen, have discovered the cause of the 

 different results which have been obtained in experiments 

 to determine the effect of high temperatures on the radio- 

 active properties of substances. They find that if the 

 experiment is made with the radio-active material in a 

 new quartz tube, change of temperature appears to have 

 no effect on the activity of the substance, and that the 

 apparent effect obtained with an old tube is due to the 

 diffusion into and through the material of the tube of 

 the products of decomposition — radium B and C. Although 

 the authors have not yet completed their experiments, they 

 consider they have sufBcient evidence to justify the state- 

 ment that for changes of temperature up to 1500° C. no 

 change of the radio-active properties of substances can be 

 detected by the most sensitive instruments. 



It is a well-known fact that when a saturated vapour 

 below its critical temperature has its volume suddenly 

 decreased, some of the vapour is condensed on the walls of 

 the containing vessel, and. in running down them, gives the 

 appearance of ripples. In the Physical Review for .August, 

 Messrs. W. P. Bradley, A. W. Browne, and C. F. Hale, 

 of the Wesleyan University, Middletown, Connecticut, show 

 that the phenomenon of ripples is also exhibited when the 

 same experiment is carried out with vapour above the 

 critical temperature. They consider that this observation 

 supports the theory that at and above the critical tempera- 

 ture the miscibility of liquid and vapour is unlimited, while 

 below it is limited by the existence of a saturation point. 

 On this view the " area of liquefaction " of the Andrews 

 diagram is really the " area of saturation " ; outside it on 

 the side of large volumes liquid may exist, but not in 

 sufficient quantity to saturate the vapour, while outside for 

 small volumes vapour may exist, but not in sufficient quantity 

 10 saturate the liquid. 



Increased importance is year by year attached in our 

 elementary schools to simple instruction in the elementary 

 rules of healthy living. Many easy reading books have 

 been produced to assist teachers in this direction, and 

 among these is Mr. W. Taylor's " First Reader in Health 

 and Temperance," a new edition of which has just been 

 issued by Messrs. George Philip and Son, Ltd., and the 

 Church of England Temperance Society. 



A USEFUL catalogue dealing with apparatus suitable for 

 chemical lecture experiments and various forms of lecture 

 lanterns has been received from Messrs. A. Gallenkamp 

 and Co., Ltd. It includes particulars of all the equipment 

 necessary for the performance of the experiments described 

 in the better-known books dealing with chemical lecture 

 demonstrations. In addition to the illustrations and par- 

 ticulars as to the sizes and prices of the instruments, the 

 catalogue provides many hints to teachers as to the way 

 the apparatus should be used and the purposes to which 

 it may be put. The list also contains information con- 

 cerning the supply of compressed oxygen, and particulars 

 respecting liquid air an-d the apparatus employed in 

 handling it. 



On previous occasions we have referred in terms of 

 praise to special catalogues, like that of books on the 



