ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
549 
river, which, however, does not give them any power, that being 
furnished by a steam engine. 
The establishment was begun in 1859 as a spectacle factory, and has 
gradually increased until it is now one of the largest in the world 
devoted to making optical goods. There are at the present time 44,500 
square feet of floor space, and about 500 hands are employed, and an 
addition is in process of construction which will add about 62,000 feet in 
area, and about 200 hands to the present plant. The new part will 
contain a Harris-Corliss engine of 500 horse-power that will furnish 
power for the entire establishment. Spectacle glasses, Microscopes, and 
photographic goods are the principal lines of work. 
Until this year optical glass was all imported, but its manufacture 
has now begun in this country, and the first exhibit of American made 
optical glass was opened at this meeting in the hall of the Rochester 
University. Discs were shown 30 cm. in diameter and 4 cm. thick, free 
from striae and perfectly annealed, made by the firm of Geo. A. Macbeth 
and Co., of Pittsburg, Penn. These discs are first ground on opposite 
sides so that they can be looked through to see if they are perfect, and 
are then stored till wanted. For some lenses the glass is pressed into 
nearly the shape required. A pair of small scales were shown with a 
piece of flint-glass on one side and a piece of crown three times as large 
on the other, and yet the scales balanced, that being nearly their relative 
specific gravities. 
The general methods of making lenses are nearly the same for all 
kinds. It consists of making a pair of metal patterns or shells having 
the shape of the surface of each side of the lens, and then cementing the 
rough lens to one with pitch, while the other is rubbed over it with the 
aid of grinding powders of different degrees of fineness. First coarse 
emery is used, then fine emery, then rouge. The latter is merely a 
particular kind of iron oxide, some forms of which are also known as 
Venetian red. Every particle of a coarser powder must be carefully 
washed off before a finer is applied, or scratches would result. 
The finer Microscope lenses have to be made by hand, one by one, 
the laps or shells being on the end of little handles not larger than lead 
pencils, and the opposite lap being kept wet with ice-water, and rapidly 
turned by a spindle in the bench before the workman. Sets of finished 
glasses lying in the boxes look like gems. The metal-work of Micro- 
scope stands is made very largely by milling machines and turret lathes. 
The first are run with high speed and slow feed, to finish with one cut 
instead of two, the single cut leaving the work finished. The turret 
lathes carry all the tools required to finish a given piece, say an adapter, 
on a revolving tail stock, whereby a slight turn brings each one suc- 
cessively into action. 
Arrangements are now being made to cut the racks on the better 
class of Microscopes with a spiral tooth, similar to that used for some 
time on the Zeiss instruments. 
This brief description is not intended to be complete, but only to 
touch on those points likely to be of interest to the members of our 
Society.” 
