256 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Microspectroscope.* — This raicrospectroscope (fig. 38), made by 

 Adam Hilger, can be substituted for the eye-piece in any form of 

 Microscope. It has an adjustable slit, comparison prism, and clip for 



test-tube to hold comparison liquid, condensing 

 lens, collimating lens, and compound prism. A 

 photographic scale and screen adjustment for 

 setting the same to the fiducial reading, and 

 mirror for illuminating the scale from any source 

 of light, are also supplied. 



Plug Micrometer.f — H. Hippie describes a 

 plug micrometer (fig. 39), having a hardened 

 bushing, H, with three holes to receive the balls 

 K. The bushing H is inserted in the barrel B. 

 The holes in the barrel are bored rather small, 

 so that at most only one-third of the diameter 

 of the ball can project. The barrel B is gradu- 

 ated longitudinally, and threaded inside to re- 

 ceive the pin S. This pin is provided at one 

 end with the cone C, and is fixed in the sleeve 

 M, which is graduated. By turning the sleeve M, 

 the pin will screw forward or backward, its cone 

 C forcing the balls K outward or letting them 

 come inward. In measuring a hole the pin S is 

 screwed out so far that the balls do not project, 

 through the barrel B, therefore resting on the smallest diameter of the cone 

 C. Then the instrument is inserted in the hole that is to be measured, and 

 the pin S is screwed in so far that the ballstouch the side of the holes. 



Fig. 38. 



„ Pill s T ^^3-(7 



G H 



Fig. 39. 



The diameter is then quickly read on the scale. The accuracy of the 

 instrument is dependent on (1) the thread, (2) the cone, and (3) the 

 balls. The smallest instrument is made for a hole from 6-7 mm. 

 (0*25 in.) in diameter. It is therefore necessary to have a number of 

 instruments in order to measure holes of greatly varying diameters. 



Gaidukov, N. — Ilunkelfeld-beleuchtung und Ultra-mikroskopie in der Biologie 

 and in der Medizin. 



Jena: Gustav Fischer (]910) 83 pp. (5 pis. and 13 figs.). 



Lowe, F. — Ein tragbares Interferometer fur Flussigkeiten und Gase. 



Zeit. f. Instrumentenkunde, xxx. (1910) pp. 321-9 (7 figs.). 



* Adam Hilger, Ltd., Catalogue, 1911, Section J, p. 3, fig. 4. 



t American Machinist, through Eng. Mechanic, xcii. (1911) p. 581. 



