64 Lieut. -Colonel Strachey on the Action of 



in public discussion has been, that all the evidence at command 

 tended to show that by an increased exercise of muscular power 

 there was, with increased requirement for respirable material, pro- 

 bably no increased production and voidance of urea, unless, owing 

 to excess of nitrogenous matter in the food, or a deficiency of 

 available non-nitrogenous substance, or diseased action, the nitro- 

 genous constituents of the fluids or solids of the body were drawn 

 upon in an abnormal degree for the supply of respirable material. 

 From the facts briefly summarized in the foregoing pages, it 

 will be obvious that the generally accepted views in regard to 

 the adaptation of food, according to its composition, to the 

 various exigencies of the animal body, require modification in 

 other respects than in so far as they relate to the source or 

 development of muscular power alone. At the same time we 

 hail with much satisfaction the confirmation of the views we 

 have so long maintained on the point (in opposition to general 

 authority) which has recently been afforded by the results of 

 the interesting, though limited experiment of Professors Fick 

 and Wislicenus, so ably discussed by them in their paper, and 

 by Professor Frankland in his lecture. 



IX. On the Action of Aqueous Vapour on Terrestrial Radiation. 

 By Lieut. -Colonel Strachey, F.R.S.* 



THE soundness of Dr. TyndalPs conclusions as to the effect 

 of watery vapour in the air on the passage of radiant heat, 

 has, I understand, been disputed by some high authorities. The 

 testing of these conclusions by observations made with no refer- 

 ence to the question at issue, will therefore probably be interest- 

 ing to persons who have followed Dr. TyndalPs admirable and, 

 as it seems to me, altogether satisfactory researches. Some- 

 thing of the sort has already been undertaken, and the results 

 have been published in the Philosophical Magazine. My own 

 method of examination is somewhat different from that to which 

 I thus refer, and seems, in some respects at least, preferable. 

 The views which I shall now briefly state were, I may add, adopted 

 some little time back, in the course of an investigation on an- 

 other meteorological problem. 



In examining the character of the diurnal variation of the 

 barometrical pressure as recorded in the Madras Observations, 

 and in considering the probable connexion between the variations 

 of pressure and those of temperature, it became apparent to me 

 that the principal cause of the increased or diminished range of 

 air-temperature was to be found in the greater or less degree of 

 clearness of the sky in the various months of the year. Follow- 

 ing up this idea, I further saw that the degree of cloudiness 

 of the sky was greatly dependent on the quantity of vapour in 

 * Communicated by the Author. 



