XXXVIll REPORT 1855. 



Apparatus similar to that employed at the Kew Observatory for the veri- 

 fication of barometers and thermometers, has been ordered by the Board of 

 Trade, for the observatory at Liverpool ; it has been constructed by Mr. Adie, 

 under the advice and direction of Mr. Welsh ; the original patterns used in 

 making the Kew apparatus having been lent for that purpose. The Committee 

 have also been informed that it is the intention of the Admiralty to provide 

 similar apparatus for Portsmouth and Plymouth. 



The apparatus necessary for the complete registration of Dr. Robinson's 

 Anemometer is in progress at the Observatory ; the castings of all the parts 

 and most of the wheel-work being completed. 



The following letter having been addressed by Mr. Welsh to the Chairman, 

 copies were forwarded, by the instructions of the Committee, to Admiral 

 Beechey and Captain FitzRoy at the Board of Trade. 



" Kew Observatory, Aug. 27, 1855. 



" My dear Sir, — I enclose a memorandum of the number of meteoro- 

 logical instruments which during the past years have been verified for the 

 meteorological department of the Admiralty and Board of Trade, with the 

 sums due to the Kew Committee for the same. 



" In the event of further contracts being entered into with the opticians 

 for the supply of meteorological instruments which are to be examined at 

 this observatory, I would offer one or two suggestions with regard to the 

 instruments and the terms of the contracts, with the view of facilitating our 

 proceedings and of securing greater uniformity in the quality of the instru- 

 ments, and greater punctuality in their delivery. 



" 1st. As regards the accuracy of the graduation of the thermometers, we 

 have, I think, been fully successful ; the instruments made by Casella and by 

 Negretti and Zambra have in this respect been constructed with much care, 

 and the numbers rejected on account of error very small. I have not, how- 

 ever, been so well satisfied with regard to the uniformity of the instruments 

 in a mechanical point of view : — the diameter of the bulbs has been too 

 irregular, and in many cases considerably more than is desirable, — the range 

 of the graduation has differed in many instances excessively from that pre- 

 scribed in the instructions of the Kew Committee, — and even the dimensions 

 of the mere material have been too little attended to, at least in some of the 

 instruments more recently made by Negretti and Zambra. With respect to the 

 first two faults, as it is practically impossible to make the instruments exactly 

 to a prescribed pattern, I would suggest that certain li7nifs should be clearly 

 specified in the contracts, beyond which the instruments must not be in 

 error ; for example, ' the diameter of the bulb should be as nearly as possible 

 0*4 inch, it must not exceed 0'5 inch, nor fall short of 0*3 inch,' and ' the 

 graduation shall extend through 8| inches of the tube, and shall range from 

 about 10° to 130°, and shall not exceed the limits 0° to 140° or 20° to 130°.' 

 The dimensions of the mere materials should of course be explicitly stated, 

 and no deviation from them be allowed. In the instructions given at first 

 by the Committee, it is stated that 'fluoric or hydrofluoric acid' may be used 

 in etching the divisions : I would suggest that fluoric acid vapour alone should 

 be used. 



" 2nd. In the case of the hydrometers, it would be well if there existed 

 more uniformity in the form and dimensions of the instruments as made by 

 the three different makers employed by Captain FitzRoy. Those made by 

 Casella are, on the whole, the best adapted for practical work; their scales 

 should, however, be more open. In shape and strength they are by 

 far the best, those by Adie and by Negretti and Zambra being much too 



