340 Bain. 



the contrary, that an intermingling (in masses, it may be, but 

 still complete), must take place above, and result in an almost 

 indifferent diffusion of the vapour-laden air northwards and 

 southwards with the returning counter-trades. The fact that 

 the northern trades have a southerly motion as they enter the 

 calm zone (passing here upwards), and vice versa, may lead to 

 a slight preponderance of air (originally) from the northern 

 hemisphere in the north-westerly counter-trade, and vice versa, 

 but by no means (I should think), to anything approaching 

 the systematic intercrossing imagined by Maury. On the 

 other hand, the preponderance might lie the other way, owing 

 to the effects of collision between the northern and southern 

 trades — but without leading to the systematic return of 

 northern air to the northern temperate zone, and of southern 

 air to the southern temperate zone, conceived to take place by 

 Sir J. Herschel. 



One of the most remarkable results of observations made 

 upon rain, has been the discovery that the amount of fall at 

 any place diminishes largely as the rain-gauge is raised above 

 the level of the ground. It is not very easy to explain 

 this remarkable fact. The explanation offered by Kamtz 

 is, that a falling drop carries with it the temperature of 

 the upper regions of air, and condenses on its surface the 

 aqueous vapour present throughout the lower strata of the 

 atmosphere, as a decanter of cold water does when brought 

 into a room. And of this explanation Professor Nichol 

 remarks, that " it is not an hypothesis but a rigorous deduc- 

 tion, giving an account of all the facts as yet ascertained in 

 connection with this subject.''' But unfortunately, the expla- 

 nation, though it undoubtedly presents a vera causa, will not 

 bear the test of cc quantitative analysis." Sir John Herschel has 

 gone through the simple calculation required to overthrow the 

 theory, and points out, that if we allow to the cause the full 

 value it can possibly have (a value far exceeding that which 

 can probably be attributed to it) we obtain an effect only one- 

 seventeenth part of what is wanted to account for the pheno- 

 menon. Sir John points out also that obliquity of fall cannot 

 possibly affect the observed amount of rainfall, and he offers no 

 hypothesis in explanation of the phenomenon, and remarks in 

 conclusion, that "visible cloud rests on the soil at low altitudes 

 above the sea-level but rarely ; and from such clouds alone would 

 it seem possible that so large an accession of rain could arise.'''' 

 He refers, however, in a note, to a paper read by Mr. Baxendell 

 to the Literary and Philosophical Society of Manchester on this 

 subject, in which it is inferred that the only way of accounting 

 for the phenomenon lies in the admission of the existence of 

 water " not in the state of true vapour," but already deprived 



