24 
DR. A. WALLER’S MICROSCOPIC OBSERVATIONS 
M. Kaemtz has obtained several interesting results in making use of this mode of 
observation, which has so long been neglected by meteorologists ; by means of these 
rings he has ascertained that the average sizes of these particles vary in the different 
months of the year, and that in summer they are much smaller than in winter; the 
mean size he assigns to them is about 0‘0224 mm . 
The opinion now entertained respecting these particles of water, consists in 
regarding them as composed of small bladders or vesicles, similar in all respects, but 
their size, to the common soap-bubble. This theory is generally ascribed to 
Halley. Neither Newton nor Halley appears to have taken any steps to submit 
their hypotheses to direct observation. This was first attempted by Kratzenstein, 
whose experiments on this subject, dating from 1743, evince great ingenuity. The 
original work is very scarce in France, and not to be obtained in this country. But 
De Saussure, in his ‘ Traite sur l’Hygrometrie,’ has cited them textually, from 
whence I extract the following. “ M. Kratzenstein qui s’est beaucoup occupe de 
ces vesicules et qui a meme pretendu reduire a elle seules tous les genres de vapeurs, 
a tente de les mesurer et les a compares avec un cheveu, et il a meme cru pouvoir 
assurer que leur diametre etait douze fois plus petit. Le cheveu avait suivant M. K. 
3-^0 de pouce et par consequent ces vesicules une 3600 de la meme mesure*.” 
Kratzenstein, after measuring the diameter of these supposed vesicular globules, 
attempted to determine the thickness of the pellicle which he believed to exist around 
them, and thus states his experiment in § 4 of his dissertation : — “ J’ai pris un globe 
de verre qui avait cinq polices de diametre ; a son orifice etait adapte un robinet. En 
soufflant dans le globe j’ai comprirne Pair qui y etait contenu, puis ayant ferme le 
robinet j’ai expose le globe aux rayons du soleil dans la chambre obscure; mais je 
n’ai pu appercevoir aucune des vapeurs que j’avais fait entrer en y soufflant. Ayant 
ouvert le robinet pour faire sortir fair comprirne, j’ai vu d’abord une grande quantite 
de vapeurs qui tombaient ; mais elles ont encore disparu lorsque j’ai comprirne de 
nouveau fair qui etait dans le globe. Regardant de inaniere que moil oeil fit avec le 
rayon du soleil un angle entre 5 et 10 degr6s, j’ai apperqu avec un grand plaisir une 
suite de tres belles couleurs qui se changaient peu a peu en d’autres a mesnre que 
fair comprirne sortait de la boule. Voici la suite de couleurs telle que je l’ai re- 
marquee, rouge, verd, bleuatre, rouge, verd. Ayant mis mon oeil entre le soleil et les 
vapeurs et les ayant regarde sous les memes angles que je viens de dire, j’ai apperqu 
les memes couleurs que donnaient la reflexion, mais elles etaient dans un ordre 
inverse.” Kratzenstein supposes that these colours arose from the expansion of 
the vesicles which caused their parietes to become thinner, and to assume colours 
in the same way as the soap-bubble; he calculated their thicknesses accordingly, 
which on an average he found to be about 0‘06 mm . De Saussure, in quoting this 
experiment, states that it never succeeded in his hands, for the colours were simul- 
* Theorie de l’elevation des vapeurs et des exhalaisons demontrd mathematiquement, par M. Gottxueb 
Kkatzenstein. Bordeaux, 1743. 
