1893.] MICROSCOPICAL JOURNAL. 339 



Idokiii^' near tlie edjie ol tln^ fovcr with a inau'nityiii},' f^'lass yuu 

 will see that the oil is collected in very small sjjots dotted 

 about, leavinsjj the j^reuter part of the slide free from oil, th<' 

 cover, of course, heing (juite clean. Take off the slip and centre 

 the slide on the turn-tahle as perfectly as j)Ossihle. and then 

 turn a rin;,' of red .'••ealing-wa.x varnish. On looking at the under 

 part of the slide, you will see that it has made a perfect ring. 

 Jn a day or two the slide will be ready for a coat of black 

 asphalt or any other tough varnish, as the sealing-wax is likely 

 to become brittle with age. 



Gold-size has been recommended for sealing liquid prepara- 

 tions, but it takes so long a time to dry (I find it still tacky 

 after three months, although I have a sample more than ten 

 years old). So that it is better to use s^^aling-wax varnish in all 

 such cases where the cell contains no liquid that will attract 

 the lacquer. 



I am indebted for the means of forming this salt to Davies' 

 work on mounting. 



(To be continued.) 



A Remarkable Collection of Photo-3Iicrographs. 



By K. M. CUNNINGHAM, 



MOBILE, ALAB.\MA. 



Having recently, by a casual circumstance, had my attention 

 called to some microscopical work done by a physician re-iding 

 in Mobile in the decade comprised between the 3'ears 18G0 and 

 1870, and on account of the interesting variety of subjects treated, 

 and the period and ciicumstances of their production, I have re- 

 garded the matter as of sufficient interest to submit the infor- 

 mation for publication in your Journal in the hope that it may 

 interest your readers. 



For the f poch noted above, Surgeon-General \\'oodward, U. S. 

 A.,had probably the greatest renown as an enthusiast in develop- 

 ing a wide spread interest in the study of the diatom, through 

 its various resolutions by means of perfected lens systems, and 

 microphotographic appliances. Those wiio visited the Centen- 

 nial Exposition at Philadelphia, may recall the magnificent 

 collection of collodion positives exhibiting the colossal plates of 

 the Surgton General's skill in llie resolution of Jincd objectsand 



