32 MOUNTING OF MICROSCOPIC OBJECTS. 



excess of ^ inch, the width of the ring being about ^ of an inch. 

 This first coat must be allowed to harden thoroughly, as on this de- 

 pends all future success of the mount. If the slightest softness is 

 left, it will be sure to yield still further in hot weather, and by 

 capillary attraction run in and spoil the slide. To insure against 

 all possibility of failure, let the slide be set aside for at least 48 

 hours, or else be baked in an oven. When the cover is ready to be 

 place upon it, a fresh ring of the cement is to be run upon the top 

 of the first, extreme care being taken not to let the fresh extend 

 to the inner edge of the old cement, lest it run in by contact be- 

 tween the surfaces of slide and cover. The latter is then to be 

 placed upon the ring, centered with the forceps, and slightly pressed 

 down. A very thin coating of the cement is now to be applied 

 around the edge, and allowed- to harden, after which as many may 

 be applied, with or without colored rings, as the taste of the worker 

 dictates. 



I find that the limit of my paper is reached without having ex- 

 hausted the subject of which it treats, and the further consideration 

 thereof must be left to a future one. In my next paper, therefore, 

 I shall hope to finish this, and, at least, make a commencement on 

 mounting in fluids, a subject that I regard as far more important 

 than either balsam or dry mounts, and one in which practical hints, 

 the result of many years of experience, may prove of more value to 

 the beginner than anything I may have heretofore offered. 



It may not be amiss to say, in concluding the present paper, 

 that I have lately, after a long series of experiments, succeeded in 

 perfecting an attachment, applicable to any microscope, whereby 

 negative enlargements of all objects not requiring a greacer power 

 than Y^ of an inch, maybe readily and perfectly made by any one, 

 even totally unacquainted with photography, and from these posi- 

 tives printed for throwing upon the screen with a lantern; at an 

 infinitesimal cost of money and time. The whole process is per- 

 formed by the simple aid of an ordinary coal oil lamp, neither 

 Heliostat or any other costly form of illumination being required. 

 I shall hope to describe and illustrate this apparatus in an early 

 number of this magazine. 



