Report of the Keio Committee. 



85 



■ In addition, 134 Thermometers have been tested at the melting- 

 point of mercury. 



14 Standard Thermometers have been calibrated and divided. 



The following miscellaneous instruments have also been verified : — 



Hydrometers 356 



Anemometer 1 



A Barograph and Thermograph have been examined, and their 

 scale values determined, for the Brussels Observatory ; also a similar 

 pair of instruments for the Zi-ka-Wei Observatory, and a Thermo- 

 graph for the Japanese Government. 



There are at present in the Observatory undergoing verification, 

 19 Barometers, 182 Thermometers, 4 Anemometers, and 1 Rain- 

 gauge. 



A number of Aneroid Barometers, of a new pattern, have been 

 received from MM. Hottinger and Co., of Zurich, for comparison. 



The " Hall Mark," figured in last report, has been etched, at the 

 desire of the makers, upon a number of the Thermometers compared 

 at the Observatory. 



A Hydraulic Press especially constructed for the purpose of sub- 

 jecting Deep sea Thermometers to pressures similar to those they 

 experience when sunk to great depths, has been erected in the work- 

 shop, by Messrs. Hopkinson and Cope. It is capable of exerting 

 a strain equal to 4 tons on the square inch. Several protected Ther- 

 mometers have been found to stand this test successfully. 



Air Thermometer. — The Committee are taking steps to obtain a 

 standard air thermometer. 



The old " Royal Society " Standard Barometer, with the flint and 

 crown-glass tubes refilled by Negretti and Zambra, has been compared 

 with the Kew standard daily for several months. Its scale has also 

 been measured and its error determined. 



Comparison of Standard Barometers. — The account of the com- 

 parison of the Staudard Barometers at Greenwich and Kew, which 

 resulted in proving a close agreement between the standards of the 

 two Observatories, was published in the "Royal Society Proceed- 

 ings," vol. xxvii, p. 76. 



With a view to determine the source of small variations in the 

 correction to the working standard of the Observatory (Newman 34) 

 and the large Welsh's standards, numerous comparisons have been 

 made between the instruments, from time to time, but as yet without 

 success. 



Professor B. Stewart has had similar series of readings made 

 between the Owens College ordinary Standard Barometer and one 

 after the Kew model, also filled by Welsh's system. The results tend 

 to show a most close agreement between the two forms of instru- 



