Report of the Kew Committee. 



159 



Swan's glow lamps, lighted by electricity derived from one of 

 Pitkin's storage batteries, has been successfully employed in testing 

 the dark shades of sextants, when requisite, during the past year. It- 

 has been found necessary to replace the lamps in two instances ; but 

 the initial charge of the battery has proved capable of working them 

 throughout the whole twelvemonths without replenishing. 



Telescope Testing. — A second test plate has been procured, and 

 mounted on a portable frame, with a reflector, in order to enable the 

 examination of telescopes to be prosecuted from the optical room as 

 well as from the lawn. A detailed form of certificate has been pre- 

 pared and issued with telescopes and binoculars examined for the 

 general public. 



6 Look-out telescopes have been examined and certified for the 

 Brethren of the Trinity House. 



Normal Thermometers. — M. Benoit, the Director of the Conserva- 

 toire des Poids et Mesures, Paris, having completed his examination 

 of the three standard thermometers, and submitted his report upon 

 them to the Committee, who have placed it in the hands of Professor 

 Rucker for discussion, proceeded to examine the low-range alcohol 

 thermometer which accompanied them. Whilst conducting this 

 operation, M. Carpenter, the observer, was so unfortunate as to break 

 the tube. M. Benoit, having strongly advised that further compari- 

 sons at low temperatures should be made by means of thermometers 

 filled with toluene instead of with alcohol, has been requested by 

 the Committee to order such an instrument of M. Tonnelot, the 

 maker, and compare it with the Sevres standards before its delivery 

 in England. The mercurial standards were safely returned to the 

 custody of the Observatory by M. Carpenter in May last. 



VI. Rating of Watches. 



During the fourteen months 709 entries of watches for rating 

 were made. They were sent for testing in the following classes : — 



For class A, 468 ; class B, 153 ; and class C, 86 ; subsidiary trial, 2 



Of these 161 failed to gain any award; 49 passed with C, 140 with B, 

 327 with A certificates, and 29 of the latter obtained the highest, 

 class A especially good. 



In the Appendix will be found statements giving the results of 

 trial of the 29 watches which obtained the highest numbers of marks 

 during the year, the highest position being attained by Messrs. 

 Stauffer, Son, and Co., London. This watch was a keyless tourbillon 

 chronometer, with going barrel, which obtained the very excellent 

 total 91*6 of marks out of a possible 100. 



Marine Chronometers. — Certificates showing the mean daily rate 



