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Report of the Kew Committee* 



and the variations of rate at three different temperatures have been 

 awarded to 18 marine chronometers after undergoing the 85 days' trial. 



The Committee having had their attention drawn to the limited 

 nature of their trials for first-class marine chronometers, decided to 

 establish a second and more rigorous trial for these instruments, and 

 have now organised two classes, which are as follows : — 



Class A trial, extending over 55 days, comprising runs at tempera- 

 tures of 45°, 70°, 95° Faht. ; and Class B trials, which last for 35 

 days, and include readings at temperatures of 55°, 70 u , and 85° Faht. 

 only. For Class A tests, the individual runs are 10 days at each 

 temperature ; whilst for Class B tests, they are only 7 days each in 

 duration. 



The Committee have drawn up a special circular addressed to the 

 directors of steamship companies, calling attention to rating chrono- 

 meters, and have distributed it to the managers of all the principal 

 companies of vessels sailing from British ports. 



As the question of the rate of a chronometer under varying tem- 

 peratures is intimately related to the behaviour of the lubricating 

 material employed, when heated, the Committee asked Professor T. 

 Thorpe, F.R.S., to favour them with his opinion as to the temperature 

 to which a chronometer may be subjected to without producing a dele- 

 terious effect upon its oil. 



Non-Magnetic Watches. — Owing to the extension of the use of 

 electrical dynamometers, a class of watches provided with springs and 

 balances of palladium or some alloy, and termed non-magnetic 

 watches, has been brought into more general use ; and the Com- 

 mittee have been requested to certify as to the extent in which 

 they may be employed in the vicinity of dynamos without deterioration 

 of their time-keeping properties. 



Professor Riicker kindly undertook to arrange to conduct a 

 series of experiments with the dynamos at South Kensington, and 

 two students of the Royal College of Science, Messrs. Edser and 

 Stansfield, have already submitted a prelimiuary report to the Com- 

 mittee upon the nature and extent of the influence in the magnetic 

 field in the neighbourhood of a dynamo. The experiments are still 

 in progress. 



VII. Miscellaneous. 



Lens Testing. — In the preliminary operations necessary to conduct 

 the satisfactory examination of photographic lenses, Major L. Darwin, 

 late R.E., has been associated with Captain Abney, and, in accord- 

 ance with his suggestions, a special camera, capable of working with 

 lenses of 4 inches aperture and 30 inches focal length, has been 

 constructed by Mr. Meagher, and fitted up at the Observatory. A 



