ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



71 



above the objective, a modification of the Watson-Conrady new con- 

 denser vertical illuminator is fitted, tbe light from a 4-volt lamp and 

 dry battery being directed to this reflector through a condensing lens. 

 It is important to note tbat the relative positions of the light, the re- 

 flector, etc., are all fixed and cannot be disturbed, so that the whole in- 

 strument is in working order directly the light is switched on. Any 

 objective, high or low, can be used, but the power usually recommended 

 is | inch. 



Winder's Special Metallurgical Microscope for Observing Struc- 

 ture of Metals under Strain.* — This instrument has been designed 

 by B. W. Winder, and is made by Messrs. Watson. It is intended to 



Fig. 6. 



work in conjunction with a testing-machine during the time that metal 

 is being tested for its breaking-strain. A testing piece, which has been 

 duly shaped and etched, is placed in the jaws of the testing machine and 

 the Microscope is focused upon it so as to observe and note, either 

 visually, or by projection or photographically, the molecular changes 

 which take place. To accomplish this the Microscope must be sup- 

 ported so as to be unaffected by the vibrations of the testing-machine, 

 and by the shock when breakage takes place. During the process the 

 test-piece of metal becomes gradually stretched, and, in order that observa- 



* W. Watson and Sons' Special Catalogue : Microscopes and Accessories for 

 Metallurgy, pp. 16, 17. 



