446 [No. 4, 



Note on the coeeection of the Calcutta Standaed Baeometee 

 to the Kew and Geeenwich Standaeds — by H. F. Blanfoed. 



[Eeceived 4th September, 1871.] 

 One of the greatest drawbacks to the value of the Meteorological 

 observations that have hitherto been recorded in India, and one 

 which has gone far to render the large majority of them worthless 

 for advancing onr knowledge of the Meteorology of the country, 

 has arisen from the neglect of observers and those charged with 

 the collection of such data, to ensure the reduction of their obser- 

 vations to one common standard. Without this, it is obvious that 

 they cannot be treated comparatively, and any deductions that may 

 be attempted from a comparison of registers must always lie oj)en to 

 the suspicion that the variations they may show are not real, but 

 due to instrumental and perhaps other errors. This is especially 

 the case with registers of atmospheric pressure. As I have more 

 than once pointed out, the variations of this important element 

 are so small in India, that the persistent barometric gradient 

 of a monsoon, existing at any moment between two stations five 

 hundred miles apart, may be entirely concealed or even reversed .in 

 appearance by the uncorrected errors of the instruments in use. 

 It follows that one of the first duties of any officer who may have 

 to supervise the working of a system of meteorological registration, 

 is to ensure that the barometers are carefully compared with some 

 well known local standard, before they are used for the purpose of 

 registration ; and that the comparison be repeated from time to 

 time, in order to detect and eliminate errors, which may arise from 

 accidental disturbance or progressive deterioration. 



In Bengal, and to some extent in the N. W. Provinces and 

 Central India, the barometer by Newman, No. 84, at the Surveyor 

 General's Office in Calcutta, has been adopted as the standard to 

 which the local observations are corrected. But whether there 

 is any constant difference between this instrument and the stand- 

 ards in use elsewhere, has hitherto been a matter of conjecture. At 

 the present day, most good instruments sent out from England 

 have been compared with the Kew Standard barometer constructed 



