Proceedings, &c. t for 1883. 143 



" There is a small arrangement of shutters for closing the 

 square apertures in the base of the micrometer, and either 

 pair can be closed at will, so that only one system of wires 

 are illuminated if desirable when observing extremely faint 

 objects, or both pairs can be closed if it is desired to use 

 central illumination and a bright field. 



" As reading the micrometer heads while observing is often 

 very troublesome, requiring a hand-lamp illumination, and 

 with many observers a lens also, I have obtained a beam of 

 light from the electric lamp for this purpose. In the 

 central stopping of the lamp lens the central half-inch is 

 cleared away, permitting a beam to pass across the optical 

 axis into a small tube fixed exactly opposite to the lamp 

 tube. At the end of this is a prism which reflects the beam 

 of parallel rays upon one side of the micrometer heads to a 

 reflective surface, which illumines the reading part of the 

 heads, so that with a small reading lens fixed to the 

 micrometer, a most comfortable and convenient method of 

 obtaining the micrometer readings is supplied. 



"The intensity of the light can be modified by increasing 

 or diminishing the electric current with a simple rheostat 

 of German silver wire, controlled by the same small milled- 

 head screw that is used for diminishing the ordinary lamp 

 light for central illumination." 



Mr. Ellery stated that this instrument had been made at the 

 Observatory, and Professor Kernot remarked that it was gratifying 

 to find that the workshops of the Observatory could turn out such 

 excellent work. 



Mr. Joseph read his paper on the " Electric Lighting for Mines," 

 and exhibited some interesting apparatus used for that purpose. 



November 15th, 1883. 

 Present, the President (in the chair) and 21 members and associates. 



A ballot was taken for the election of the following gentlemen, 

 who were duly elected : — Mr. A. S. Way, M.A., as member ; Mr. 

 C. T. J. Vautin, as member ; Mr. J. L>. Ploos van Amstel, as 

 member ; Mr. F. Rennick, as member ; Mr. Bennett Hull, as 

 member ; Mr. A. T. Danks, as associate ; Mr. Frederick Smith, as 

 associate ; Mr. S. T. Magee, as associate ; and Mr. T. W. Fowler, 

 as a country member. 



The Hon. Librarian reported that he had received 1 volume and 

 48 parts of scientific works since the last meeting. 



