140 



THE AMEKICAN MOKTHLT. 



[July. 



with the eminent men of science from 

 England, whose names are famiUar to us 

 all. 



CORRESPONDENCE. 



Cement for Mounting. 



To THE Editor : — In one of your is- 

 sues you kindly referred to the finishing 

 cement used by me on my slides, but you 

 got a little astray as to the material I em- 

 ploy. I don't know anything about the 

 color you mention. As a matter of fact, 

 I use one of C. T. Raynolds & Co.'s coach 

 colors, either ruby lake or body lake, 

 which I mix with the ordinary asphalt. 

 I cannot give the proportions exactly, be- 

 cause it is a matter of experiment from 

 time to time. I mix them until I get the 

 shade and consistency 1 like. The coach 

 color, if used alone, would dry almost 

 immediately into a solid dead mass, like 

 brown putty. Mixing it with asphalt pro- 

 duces a cement which builds up easily, 

 dries rapidly, and sets firmly, with a half 

 shiny, half dead surface resembling choc- 

 olate. The coach color by itself is likely 

 to crack when dry, but the mixture never 

 cracks if properly made. I know of no 

 cement for dry mounting which has as 

 many good qualities as this one. 



C. F. Cox. 



Glycerin in Mounting. 



To THE Editor : — In regard to your 

 editorial remarks upon the use of glycerin, 

 pages 15 and 16 of current volume, apart 

 of the trouble may be deduced from this 

 sentence : ' The great value of glycerin in 

 mounting arises from its density and per- 

 fectly neutral character.' Now it is much 

 easier to find glycerin which is not per- 

 fectly neutral than vice versa. However 

 crude the test may appear, the simple ap- 

 plication to the tongue of various samples 

 of glycerin will reveal the fact. Common 

 samples of glycerin leave a distinct after- 

 taste of a fatty acid. 



Price's glycerin is free from this disa- 

 greeable taste. It is a matter of certainty, 

 therefore, that if the preparer use an acid 

 glycerin in delicate specimens, and one 

 almost surely also lacking in density, 

 chemical and physical changes are right- 

 fully to be looked for. 



I may instance a proboscis of the house- 

 fly prepared and mounted unpressed in 

 Price's glycerin two years since. Some 

 observers might say it is too transparent ; 

 no one would accuse it of granularity. 



Dr. Beale's directions for using glycerin 

 even for zoophytes are explicit. ' All that 

 is required is, that the strength of the fluid 

 should be increased very gradually [from 

 sp. gr. 1050] until the whole tissue is thor- 

 oughly penetrated by the strongest that 

 can be obtained.' ' How to Work,' 5th 

 edition, page 362. It is hard to resist the 

 conclusion that those who complain of 

 granular specimens fail in purity of 

 glycerin or in patient and faithful pre- 

 paration of specimens. 



Edward Gray, 

 A. A. Surgeon, U. S. Army. 



Device for Mounting. 



To THE Editor : — I have before me a 

 very ingenious contrivance for mounting 

 microscopic objects, devised by Mr. G. C. 

 Hinman, of this city. It consists of a per- 

 forated plate with the edges turned up so 

 as to receive a glass slip, and hold it with 

 the centre over the centre of the perfora- 

 tion, thus enabling the object to be placed 

 centrally without difficulty. When the 

 object is mounted, this plate is placed 

 upon another under a spring having three 

 points in a plane parallel with the surface 

 of the slip, which can be pressed down 

 upon the cover-glass with any desired 

 force, and thus bring the cover-glass into 

 a plane parallel with the slip. This is by 

 far the most convenient instrument for 

 holding the cover-glass in place I have 

 ever seen. 



J. H. PiLLSBURY. 



June ist, 1884. 



Exchanges. 



Exchanges are inserted in this column without charge. 

 [They will be strictly limited to mounted objects, and 

 material for mounting.] 



Echinus spines of various species offered to an)' 

 person who will send in return three good sections 

 of the same. 



Box 630, Washington, D. C. 



Wanted — Diatoms on seaweeds and in muds, from 

 all the tropic seas. Offered a large quantity of fine 

 selected diatoms and other slides, or cash. 



J. C. RINNBOCK, 

 14 Simmering, Wien, Austria. 



Will exchange well mounted slides for others well 

 mounted. 



H. H. PEASE, 

 1271 Broadway, N. Y. 



Living red Astasia neemaiodes {Eug'iena viridis) 

 and Volvox sent on application, or mounts of the same 

 in exchange for algse, fungi, or infusoria. 



J. M. ADAMS, 

 Watertown, N. Y. 



Will exchange various mounts of crystals for other 

 slides, and material for mounting. 



JAMES E. WHITNEY, 



Rochester, N. Y. 



