Report of the Kew Committee. 



97 



made by means of a Negretti and Zambra's Standard, No. 1042, 

 which he found at Pesaro, and which had been compared at Kew in 

 1877. By means of an indirect comparison of this instrument with 

 the Standard, Deleuil No. 6, at Rome, he found the correction of the 

 latter, so referred to the Kew Standards, to be —0*23 millim. 

 ( — 0*009 inch). Subsequently, Professor Tacchini conveyed another 

 barometer directly to Kew, and this when compared with the Roman 

 Standard, indicated the difference between the two instruments to be 

 —0*19 millim. (—0*008 inch). From these two comparisons he 

 assumes the true correction of Deleuil No. 6 to be —0*21 millim. 

 ( — 0*008 inch). Having already determined the correction of that in- 

 strument referred to the St. Petersburg Standard to be —0*22 millim. 

 (—0*009 inch), he concludes that the two absolute Standard Baro- 

 meters of Kew and St. Petersburg perfectly agree, and taking into 

 account the possible error of reading the instrument at Rome, "they 

 cannot differ between themselves more than half the tenth of a 

 millim. (0*002 inch)." With the absolute Standard of the College de 

 France he found the correction of Deleuil No. 6 to be —0*18 millim. 

 ( — 0*007 inch). Hence he also concludes that the absolute Standard 

 Barometer of the College de France perfectly agrees with the absolute 

 standards of Kew and St. Petersburg within the limits of the half-tenth 

 of a millim. (0*002 inch). 



VI. Miscellaneous. 



Waxed Papers, Src, supplied. — Waxed paper has been supplied to the 

 following Observatories : — 



Colaba, Toronto, Mauritius, and the Meteorological Office. 



Anemograph Sheets have been sent to Mr. Pogson, Madras 

 Observatory. 



Blank Magnetic Observation Forms have been supplied to Pro- 

 fessor Brioschi, Naples. 



Two glass tabulating scales for measuring magnetograph curves 

 were constructed for the Toronto Observatory, and five various glass 

 scales for the Hong Kong Observatory. 



Two Additional Divided Plates for the Sun Picture Micrometer 

 have been supplied to the Mauritius Observatory. 



A Thomson Quadrant Electrometer was procured from the maker, 

 and after examination, forwarded to Senhor Capello, of Lisbon. A 

 portable Thomson Electrometer has also been purchased, and had its 

 scale value determined for M. le Directeur de l'lnstitut Technique et 

 Nautique de Bari, Italy. 



Magnetic Survey of Great Britain and Ireland. — The attention of the 

 Committee having been called to the fact that twenty-four years have 

 elapsed since the surveys of Sabine and Welsh were completed, and 



VOL. xxxvi. h 



