70 



H. F. Blaiiford — 0?? Atmosplirric Pressure [No. 1, 



P. S. June 2Qt'h, 1880. — After the earlier part of this jmper was 

 drafted, I learnt that M. St. Claire Deville had proposed to make standards 

 of the Commercial Kilogram in a new manner. The metal is to be the 

 Platinum-iridium alloy so as to secure hardness and indestructibility, but, in 

 order that tlie density may be nearly that of brass, it is to be hollow, the 

 parts are to be soldered together by fusion so as to enclose a constant 

 mass of air, which, of course, will be included in the weighings. This plan 

 has been adopted by tlie International Commission for making the Euro- 

 pean Metric Standards, and will no doubt be a great improvement on the 

 old Commercial Standard of France, which is made of brass. The volume 

 of these weights is to be 125 cubic centimetres, so that the density will be 

 8-0 ; which is a little lower than that of good sound weights of brass, and 

 materially lower that that of gilt bronze ; while it is greater than that of 

 iron. 



Certainly, the visible Commercial unit, to which reference can be made, 

 appears preferable to the imaginary unit of England. Such a weight 

 would vary in Calcutta with respect to the scientific unit to the extent of 

 about 11 milligrams, and it would be needless to take notice (for commer- 

 cial purposes) of the much smaller variations with respect to such weight 

 as may be compared with it. 



VI. — On tlw High Atmospheric Pressure of 187(5-78 in Asia and Australia, 

 in relation to the Sun-spot Cycle. — By Henry F. Blanford, Met. 

 Bep. to the Govt, of India. 



(Received December 24th, 1879 ; Eead January 6th, 1880.) 

 (With Plate I.) 



The three years 1876, 1877, and 1878, more especially the two former, 

 were characterized by a deficiency of rainfall in one or many parts of India, 

 and by a more general and very persistent excess of atmospheric pressure. 

 With but slight and local interruptions, from August (in some parts of 

 India from May) 1876 to August (in some cases only to May) 1878, over 

 the whole of the Indian area, the barometer ranged above the average of 

 many years. Nor was this excess of pressure restricted to the land. The 

 register of Port Blair at the Andaman Islands, and that of Nancowry at 

 the Nicobars, shew that, at these insular stations, the excessive pressure was 

 of greater duration and more persistent and intense than at any continen- 

 tal station at or near the sea-level ; indeed, with one striking exception, 

 more intense than at any other station in the entire region. At these 

 islands, the pressure rose above the average in May 1876 ; and, from that 

 tune to August 187S inclusive, the mean pressure of every month was from 

 001" to •071" in excess of the average ; derived, in tlie case of Port Blair 



