PHYSICS OF THE GLOBE. 151 



ously noted, also the " Tables " for the use of observers. 

 In the latter Blanford gives especial attention to the tables 

 to be used with the dry- and wet-bulb psychrometer, which 

 tables he has compiled for the altitudes 300, 2000, 4000, and 

 7000 feet. So far as regards relative humidity, these can be 

 used in other countries as well as in India; but as regards 

 vapor tensions, they are specially adapted to the latitude 

 22, in order to allow for the variation of gravity. This 

 slight correction was, according to Blanford, first applied by 

 Robert Dixon. 



According to Markham, in 1872, Dr. Forbes Watson, the 

 Reporter on the Products of India to the Secretary of State, 

 prepared an elaborate paper on the Conditions under which 

 the Wet- and Dry-bulb Barometers should be Exposed, in or- 

 der to give Accurate Results as a Hygrometer. This paper 

 represents a vast amount of laborious work and careful 

 thought, and the tables of observation that accompany it 

 tend to show that the results hitherto obtained by the use 

 of the wet and dry bulbs are nearly worthless. Dr. Watson 

 suggests steps that should, be taken to ascertain the condi- 

 tions under which it may be possible to obtain reliable re- 

 sults. Mr. Buchan has expressed his sense of the great 

 value of Dr. Watson's memoir, and that it ought to be in 

 the hands of every meteorological observer, but it has not 

 yet been printed. 



A paper on an Improvement in the Hair Hygrometer was 

 read by Dr. Nippoldt before the German Association at Cassel. 



A modified form of hygrometer, in which the quantity of 

 aqueous vapor is directly determined by a volumetric proc- 

 ess, has been constructed by Schwackhofer for Dr. Lorenz 

 and the Agricultural High-School at Vienna. This " volume 

 hygrometer" has of late been employed in a series of hourly 

 observations, for which it proves to be very convenient. The 

 accuracy attained by it is one hundredth of one per cent, of 

 the volume of vapor. The apparatus is equally accurate at 

 all temperatures, and in high winds or in calms. It can also 

 be used to determine the quantity of moisture present, as fog 

 or cloud. Its price, however, is about $100. 



In the quadricentennial volume of "Meteorological Obser- 

 vations" published at Upsala, Rubenson gives some notes as 

 to investigations into instruments and methods. He finds 



"o 1 



