38 



THE AMERICAN MONTHLY 



[February, 



with four or live times its volume 

 of water. To fix the carmine, a 

 mordant is prepared as follows : 

 A. 10 grains of aliiminic sul- 

 phate are dissolved in 200 

 grains of water. jB. 30 grains of 

 sugar of lead are dissolved in 600 

 grains of water. Add ^ to ^ 

 until precipitation is complete, al- 

 low to settle, and draw off the clear 

 liquid. When required for use 

 dilute with 4-5 parts of water. 



The anilin solution is made by 

 dissolving 3 grains of iodine-green 

 in 1 ounce of absolute alcohol. 



The process of double-staining 

 is as follows : 



The bleached sections are placed 

 in the mordant for several hours, 

 from which they are transferred to 

 the carmine, where they remain an 

 hour or so, and are then washed and 

 placed in alcohol. 



The sections are then soaked for 

 twelve hours in the anilin, then 

 transferred to absolute alcohol for 

 a few seconds only, then to oil of 

 cloves, in which they must remain 

 only long enough to become trans- 

 lucent, then mounted in balsam 

 dissolved in benzole. 



Undoubtedly, a one per cent, 

 solution of alum would answer for 

 a mordant quite as well as the 

 solution prepared as directed above. 



CORRESPONDENCE. 



To THE Editor: — I doubt not that 

 many of your readers who are interested 

 in the preparation of diatoms and spicula, 

 have desired a more handy method than the 

 only one I have ever seen prescribed in 

 the treatises on such subjects, viz. : the 

 boiling in muriatic and nitric acids. In 

 your No. 1, just received, Mr. Paul Petit 

 describes a plan for cleaning diatoms zn 

 situ on sea-weed. I think if he will try 

 my plan he will jfind it the more easy of 

 the two. To clean diatomaceous earths 

 (not containing a large percentage of lime) 

 sea-weeds, and the ordinary collections 

 from ponds, etc., I dry them in any con- 



venient way and then mix them in a plati- 

 num crucible, with rather more than an 

 equal bulk of pure bi-sulphate of potash, 

 and fuse for 5 minutes at a bright red- 

 heat over a Bunsen burner. Such materials 

 as the Jutland cement stein, and guano, 

 which contain a large quantity of lime, I 

 first soak in muriatic acid in a test-tube 

 until all action ceases, wash, and then fuse 

 in the bi-sulphate of potash. In all cases, 

 after fusing in the bi-sulphate of potash 

 allow the mass to cool in the crucible and 

 then place crucible and all in a beaker of 

 water which will dissolve the bi-sulphate 

 and leave the diatoms and other silicious 

 matter free from alumina and organic 

 matter. Wash with clean water, until there 

 is no acid reaction with litmus paper, and 

 then separate the diatoms from the sand, 

 as usually directed. The advantages of 

 this plan I have found to be, freedom 

 from the injurious fumes of boiling nitro- 

 muriatic acid, and also from the liability to 

 spurt the acid out of the test-tubes. The 

 diatoms are clean and white, requiring no 

 bleaching with chlorate of potash, and the 

 work is all done with one operation, except 

 when the materials contain lime. Even 

 from guano the silica will all come out 

 white and clean. Owing to the common 

 use made of bi-sulphate of potash by 

 chemists for similar operations, I can 

 hardly suppose that this process is new 

 and have been surprised that I have not 

 found it in books treating of the prepar- 

 ation of such material. With diatoms 

 in situ on sea-weed I have sometimes 

 burned the material before adding the bi- 

 sulphate. 



Galloway C. Morris. 

 Germantown, Pa. 



To THE Editor: — I notice that in 

 July, 1876, Dr. Wythe had in his posses- 

 sion an amplifier which consisted of a 

 double-concave lens, and which he reported 

 as nearly doubling the power of an ob- 

 jective, while it gave excellent definition. 

 I had one made by Zentmayer, that came 

 with a Zentmayer's " army hospital " 

 stand (price, $8,) and liked it very much ; 

 this was in 1877-8. Is this not the same 

 as Dr Wythe's ? It screwed into the lower 

 end of the draw-tube and was fitted with 

 the society-screw, so that it could be 

 used with any microscope arranged to 

 receive a low-power objective in the end 

 of the draw-tube, and could readily be 

 fitted to any draw-tube. 



S. A. Webb. 



Oswego, N. Y., Dec. 22d, 1879. 



