THE MICROSCOPE. 5 
Mr. Tolles was born in Connecticut sixty-two years ago, but 
at an early age went to New York, where, while yet a young man, he 
entered the employ of the firm since widely known as Spencer & 
Son, optical-instrument makers at Canastota, with whom he learned 
the business of grinding lenses and the mechanical construction of 
microscopes and telescopes. After being with that firm a number 
of years, he set up for himself in the same line of business in the 
same town. He remained there until 1866, when he came to 
Boston,and,in connection with Mr. Chas. Stodder founded the Boston 
Optical Works, which business connection continued until his death; 
and it was here that the most of his reputation as a maker of first- 
class objectives for the microscope was achieved. He was among 
the first to produce what are known as wide angle objectives, and to 
demonstrate their superiority in showing the finer details of the 
structure of objects. Although not the discoverer of the immer- 
sion objectives, he at once recognized their great value, and was 
among the first to manufacture them. 
Mr. Tolles was the inventor of many valuable accessories both of 
the microscope and telescope, but undoubtedly his greatest achieve- 
ment in this direction was his demonstration of the practicability of 
the homogeneous immersion objective and its superiority over 
other lenses. This he demonstrated in 1871, but owing to the fact 
that at that time Canada balsam was the only fluid known to possess 
the same refractive index as crown glass, his discovery remained 
useless until 1877, when Professor Abbe discovered a fluid which 
was practical for such a purpose. Since then a large number of 
such objectives have been made and numerous discoveries made by 
their use which would have been impossible with the old water im- 
mersion lenses. 
Mr. Tolles was a very quiet, unassuming gentleman, who 
devoted his whole life to his work. He had not been in health for a 
long period of time, having been a sufferer from a chronic lung dis- 
ease to which most men would have succumbed years ago. In his 
death the scientific world has sustained a great loss. ; 
Dr. Geo. E. Blackham writes from Dunkirk, N. Y.:— 
The loss to microscopy throughout the whole civilized world is 
simply irreparable; but to us who had the happiness to be counted 
among his personal friends there is something more than the mere 
