THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



APRIL 1858. 



XXXI. On the Forms of Clouds. 

 Bi/Vl. S. J Evoss, Assaijer, Sydney Branch of the Royal Mint*. 



[With a Plate.] 

 1. TN the Philosophical Magazine for July 1857, will be found 

 -1- a paper " On the Cirrous Form of Cloud,^^ in which I 

 attempted to show, from a simple experiment, that cirri are pro- 

 duced by the interfiltration of bodies of moist air, merely differing 

 in temperature. Simple differences of specific gravity, and 

 motions thence resulting, might, however, be said to be the actual 

 cause of the cirrus. Having since followed out the same mode 

 of investigation into more complicated and perhaps more inter- 

 esting cases, I have now to publish the results to which I have 

 been led concerning the cumulus, the cumulostratus, and the 

 nimbus or thunder-cloud. It will be well, however, first of all, 

 to state distinctly the nature of the evidence and arguments 

 which I shall adduce. 



2. Now the means by which I take the first step to explain 

 the form of a cloud, is to produce experimentally with liquids a 

 miniature representation of it, under conditions in which the im- 

 mediate causes can be certainly known. If it is found that given 

 portions of liquids of ascertained specific gravities, when placed 

 together or variously set in motion upon eacli other, produce 

 peculiar appearances which exactly resemble in form some of the 

 more distinct kinds of clouds, I assume with complete confidence 

 that similar motions and differences of specific gravity have ope- 

 rated in the production of the atmospheric clouds in question. 



It must be distinctly understood, that in this first step we are 

 dealing only with dynamical causes, that is, with simple force 

 * Communiciited by the Author. 



Plul, May. S, 4. Vol. 15. No. 100. April 1858. R 



