504 Journal of Applied Microscopy. 



system is to displace the old analysis in the wet way, every chemist should, 

 nevertheless, familiarize himself with the microscope, its accessories, and the 

 elegant and time-saving methods of micro-analysis, thus enabling him to examine 

 qualitatively the most minute amounts of material with a rapidity and accuracy 

 which is truly marvelous ; not to speak of the many substances for which no 

 other method of identification is known. 



At present the greatest bar to its general use is the absence of any well de- 

 fined scheme, and the absolute necessity of being well grounded in general 

 chemistry. There are no tables which can be followed in a mechanical way by 

 the student, but on the contrary he is obliged to exercise his knowledge and 

 judgment at every step. For this very reason the introduction of this subject 

 into the list of those now taught is greatly to be desired. 



Thoroughly convinced of the desirability of chemical students becoming 

 familiar with the essential features of micro-chemical methods, and of their 

 obtaining some little practice in these methods, the writer deemed it advisable to 

 offer a regular course of work in this subject. Not a course in the manipulation 

 and use of the microscope, but in practical micro-chemical analysis, with special 

 reference to the examination of minute amounts of material and the application 

 of this system to the identification of substances which can be detected in no 

 other way. 



At the very outset a most serious obstacle was encountered, the absence of 

 any convenient microscope. There is no doubt that regulation petrographical 

 stands would have answered admirably, but the expense clearly placed them out 

 of the question. These stands were also needlessly complicated for the work to 

 be done. That which was wanted was a compound microscope of as simple 

 construction as possible and fitted with only such accessories as were essential 

 to the work in hand. It was also necessary that the instruments be inexpensive. 

 The foreign instruments now supplied for this class of work did not seem 

 wholly satisfactory. Negotiations were therefore begun with the Bausch & Lomb 

 Optical Co., regarding the construction of a special stand at a low price, which 

 would fulfill certain specifications, the details of construction being left to them. 

 Thanks to the courtesy and kindly interest of this firm, a neat, efficient instru- 

 ment has beeen placed on the market. The writer wishes particularly to 

 acknowledge the excellent manner in which they worked out his suggestions. 



At present as in use in our laboratory, where it is giving much satisfaction, 

 the instrument is arranged as follows : (See fig.) 



The stand, as will be seen by the accompanying cut, is of the continental 

 type. Since in all the work for which it is intended, the stand is always used in 

 an upright position, it was not thought necessary to provide it with a jointed 

 pillar. The coarse adjustment is by rack and pinion, the fine by micrometer 

 screw. The stage is circular, rotating, provided with centering screws ; its cir- 

 cumference is graduated into degrees for measuring crystal angles. 



The stage is faced with hard rubber. The substage is adjustable by means 

 of a quick-acting screw. Into the substage is fitted the polarizing apparatus 

 consisting of a Nicol prism of large size and so mounted that by means of a pin 

 fitting into a slot in the substage ring, the prism can always be replaced in 



