536 



SCIENCE. 



[N. S. Vol. XVII. No. 431. 



Aniline 12 parts. 



Hydroclilorie acid 18 



Water q. s. 100 " 



or 



Aniline hydrochlorate 15 



Water q. s. 100 " 



Solution 2 has not been changed except 

 to arrange the parts per hundred. 



The method of application is the same 

 except that after solution No. 1 has dried, 

 the excess of the solution which has dried 

 upon the surface of the wood is thoroughly 

 rubbed off before the application of solu- 

 tion No. 2. The black color does not ap- 

 pear at once, but usually requires a few 

 hours before becoming ebony black. The 

 linseed oil may be diluted with turpentine 

 without disadvantage, and after a few ap- 

 plications the surface will take on a dull 

 and not displeasing polish. The table 

 tops are easily cleaned by washing with 

 water or suds after a course of work is com- 

 pleted, and the application of another coat 

 of oil puts them in excellent order for an- 

 other course of work. 



Strong acids or alkalies when spilled, if 

 soon wiped off, have scarcely a perceptible 

 effect. 



A slate or tile top is expensive not only 

 in its original cost, but also as a destroyer 

 of glassware. Wood tops when painted, 

 oiled or paraffined, have objectionable fea- 

 tures, the latter especially in warm weather. 

 Old table tops, after the paint or oil is 

 scraped off down to the wood, take the 

 finish nearly as well as the new wood. 



A Useful Light for Biological Labora- 

 tories: E. A. Andrews, Johns Hopkins 

 University. 



Experiments at the seashore and in this 

 laboratory show that acetylene lamps have 

 some advantages over other artificial lights 

 for use with the microscope when good 

 daiylight is not available. These are : less 



irritating character of the light, greater 

 whiteness, that enables color to be justly 

 judged, and portability. With these is 

 joined an intensity sufficient for use with 

 Zeiss 18-ocular and 2-mm. objective. 



The Welsbaeh light with Eisen's color 

 screens* gives excellent results, but the ani- 

 line screens are troublesome, the mantles 

 fragile and a gas supply not everywhere 

 available. 



The electric lamps as used by Metcalf f 

 are exceedingly convenient, but less power- 

 ful and less white than the acetylene lamp. 

 Some of the better acetylene bicycle 

 lamps give good results for the individual 

 worker; but, till the market be supplied 

 with a lamp specialized for our purposes, 

 the best lamp for individual and for class 

 use seems to be the acetylene lamp known 

 as the 'Blectrolite.' To adapt this to mi- 

 croscopic work we add a 'bobeche' as used 

 for Welsbaeh lights, made of finely ground 

 imported glass. There is also added an 

 opaque shade, instead of a globe, large 

 enough to restrict the light to the area of 

 the table in use. All the light used passes 

 through the ground glass and is diffused. 

 For use with high powers and vertical 

 stand the too tall lamp may be placed 

 lower than the work table. On the other 

 hand, for a class using low powers the tall 

 stand will spread the light, so that ten or 

 twelve using Zeiss D and ocular 2 may 

 work around one lamp if the tables are 

 properly placed. 



The objection to acetylene lamps is the 

 trouble of attending to them, but in the 

 'Electrolite' filling and cleaning are not 

 difficult, and with one charge of carbide 

 the lamp may be put out and relighted 

 at any time till more than ten hours of 

 actual burning have passed. Acetylene 

 for microscopic work has been commended 



* Zeit f. loiss. Mile, 1897. 

 t Science, 1901. 



