456 Prof. 0. Michie Smith on 



of the difficulties that lie in the way of such a theory are 

 exhibited by the great differences observed in the rates of 

 somewhat analogous chemical changes. To take one example : 

 how could such a theory explain the fact that, under suitable 

 conditions of temperature and dilution, ferrous sulphate is 

 oxidized by potassic chlorate at such a rate that only a frac- 

 tion of the total work capable of being done is accomplished 

 in ten thousand minutes, whereas permanganate performs the 

 same work practically instantaneously ? Interdiffusion and 

 simple contact among the active molecules alone would seem 

 incapable of offering any explanation of this and similar facts ; 

 at the same time it would be dangerous to speculate on the 

 tendencies that chemical compounds undoubtedly possess to 

 resist or undergo change under various conditions, in the face 

 of the small amount of work that has been done bearing on 

 chemical change. 



In conclusion, I have to thank W. Crookes, Esq., F.R.S., 

 for affording me facilities for performing the above expe- 

 riments. 



LIV* Atmospheric Electricity. By C. Michie Smith, B.Sc, 

 F.R.S.E., F.R.A.S., Prof. Phys. Sc. Madras Christian 

 College*. 



IN 1882 I presented to the British Association a short 

 report on observations made on atmospheric electricity in 

 Madras, which, though few in number, were of some interest, 

 as they seemed to show that negative electrification of the air 

 \^as not necessarily associated with broken or stormy weather. 

 At the same time it may be noted that the observations vyere 

 by no means conclusive, as they were in each case followed 

 by local showers which fell some hours afterwards. Since my 

 return to India, however, I have obtained a large number of 

 observations, many of w r hich fully bear out the conclusion 

 that, even in fine weather, the air may at times be highly 

 charged with negative electricity. 



Neglecting a few single observations, the first series obtained 

 was in September 1883, when, on twelve days between the 

 3rd and 25th, negative readings were recorded. At the time 

 that these readings were taken I thought they were in some 

 way connected with the green sun and the w r onderful sun- 

 glows wdiich appeared that month ; and an account of them 

 will be found in my paper on these phenomena in the Transac- 

 tions of the Royal Society of Edinburgh, vol. xxxii. p. 389. 

 More recent observations have, however, shown that, under 

 • Communicated by the Author. 



