OF THE MICKOSCOPE. 37 



the fire, stir well until it begins to stiffen, and then pour it out 

 on a flat metal plate the surface of a smoothing iron answer- 

 ing very well. The plate of cement should be from one-half to 

 three-quarters of an inch thick, and the little globules are easily 

 fastened into it by seizing them by the small handles left on 

 them, holding them by a pair of forceps in a lamp flame until 

 they are hot enough to melt the cement, and then pressing 

 them m to about half their depth or a little more. When quite 

 cold they will be very securely held. The little handles, or tails, 

 are now nipped off with a pair of cutting pliers, and the glo- 

 bules ground all at once on a fine grindstone, or still better on 

 a metal plate charged with emery. When they have been re- 

 duced nearly to the surface of the plate of cement, they should 

 be ground with emery of the finest kind, and as soon as all 

 coarse scratches have been removed they should be polished on 

 a buff leather with crocus martis or putty powder. When finely 

 polished they may be removed from the cement by means of a 

 small chisel, and any cement that adheres may be dissolved off 

 by means of alcohol. They are then mounted in thin plates of 

 lead, brass, or, what is better still, vulcanite. Out of two dozen 

 such globules, carefully made and well polished, three or four 

 may be obtained that will give satisfactory definition, and it 

 was with such lenses that the early microscopists made many of 

 their discoveries. These men, however, took great pains in 

 making and polishing them, and rejected hundreds as unfit for 

 use. The objections to the microscopes of this kind, that are 

 ordinarily sold, are that they are badly made, and that good 

 and bad are sold together without any selection being exercised. 

 But, even if well made, they are very difficult to use, and very 

 unsatisfactory in their results, even in the hands of persons of 

 great skill. The polish of a fused surface never equals that of 

 a surface finely cut aud polished, as every housekeeper that is 

 familiar with common, and with cut glass, very well knows. 

 The fused surface of these little globes is, therefore, always 

 more or less, covered with striae or very minute ridges which 

 interfere with their defining powers, and we have described 

 thus minutely the process of their manufacture, rather for the 

 purpose of giving our readers such information as will enable 

 them to understand how they can be sold so cheaply, than in 

 the hope that they will endeavor to make them for themselvc s. 



