204 THE AMEKICAN MONTHLY [September, 



suits in Photomicrography by Improved wSubstage Illumination." 

 The lecture was illustrated with work done by the author. 



Dr. George M. vSternberg, U. S. A., gave a very entertaining 

 discourse on " Photomicrographs by gas-light," illustrated with 

 lantern views. 



At 4 o'clock the microscopists enjoyed an excursion to Lake 

 Ontario. Supper was taken at the Hotel Ontario and speech- 

 making was the order of the day. 



Thursday Morning. 



The microscopists were on hand promptly at the business 

 meeting this morning, but much time was occupied in adopting 

 a new constitution section by section. 



When this was finished Professor Clark Bell, of New York 

 city, read a paper on "■ Blood and Blood vStains." Red corpuscles 

 were first discovered in human blood in 1673. Oval and nucle- 

 ated corpuscles were found in birds and fishes, reptiles, etc., but 

 not in mammals. 



Professor William A. Rogers, of Colby University, Waterville, 

 Me., read a paper on " The Filar Micrometer." Professor Rog- 

 ers stated that in his work of investigating standards of length he 

 required a Filar micrometer of superior construction. Failing to 

 find such an instrument in the market, he asked Bausch & Lomb, 

 the well-known optical firm, to make one which would fulfil the 

 required conditions. After many trials the instrument was com- 

 pleted to his entire satisfaction. The instrument in question is 

 an eye-piece in which there is a fine spider web moved by means 

 of a precision screw. The difficulty in ordinary micrometers 

 consists in the lack of delicacy of movement of the springs which 

 press the micrometer plate against the end of the screw. This 

 difficulty Bausch & Lomb have averted. 



Professor Rogers read a second paper, on the " Use of the Mi- 

 croscope in the Workshop." The speaker stated that he had for 

 some years advocated a more extensive use of the microscope 

 in the ordinary operations of mechanical construction. His 

 paper was an enumeration of the different mechanical operations 

 in which he found the use of the microscope profitable. Among 

 those specified were : 



First, to divide an index wheel in 1,000 equal parts; second, 

 in setting the ways of a large planer horizontal ; third, to ascer- 

 tain whether a piece of planed work has its surface truly planed 

 before the piece is taken from the planer; fourth, to ascertain 

 whether the planer planed a piece of metal in a straight line ; 

 fifth, to plane two surfaces exactly alike; sixth, to set the line 

 between the centres of a lathe parallel with the ways ; seventh, 

 to test the turning of a true cylinder; eighth, to test the accu- 

 racy of the screw of a common lathe. 



As an illustration of the last point, the speaker described his 

 test of a precision screw twenty-one feet in length, made by Pratt 



