TRANSACTIONS OP THE SECTIONS. 29 



Meteokology. 



Account of an Apparatus for determining tJie Quantity of Hygrometric 



Moisture in the Air. By Dr. Andrews. 



The object of the author was to contrive an apparatus capable of giving directly 

 the amount of moisture in the air by the unerring indications of the balance, and 

 which might, at the same time, be easily employed in the physical cabinet, or other 

 place devoted to meteorological observations. For this purpose, according to a 

 method long known to chemists, a given volume of air is drawn through- a weighed 

 U-tube filled with some substance retentive of moisture ; but the author proposes 

 certain modifications in the apparatus hitherto emploj'ed which are designed to 

 render it applicable in the hands of persons not familiar with chemical operations, 

 or who may not have the convenience of a laboratory vvithin reach. With this ob- 

 ject in view, he found it necessary to reject both sulphuric acid and chloride of calcium 

 as desiccating agents, in consequence of their being either too troublesome in the 

 preparation, or unsafe in the vicinity of valuable instruments ; but an excellent sub- 

 stitute presented itself in calcined sulphate of lime or gypsum, which he ascertained 

 by numerous experiments to be capable of removing every trace of moisture from 

 air passed even in a tolerably rapid current through tubes containing it. The sul- 

 phate of lime was employed in small fragments prepared by moistening powdered 

 alabaster, as commonly used by plasterers and moulders, and spreading the moist- 

 ened mass into the form of thin plates, which were afterwards rendered perfectly 

 anhydrous by being placed on an iron plate heated nearly to obscure redness. 

 The aspirator consists of a gasometer whose bell is attached as a counterpoise to the 

 weight of a Dutch clock, sufficiently heavy to work it, by which simple contrivance 

 a known volume of air may be drawn at a uniform rate, and in any required time, 

 through the desiccating tube. The quantity of moisture in the air may, in this way. 

 be determined to almost any degree of accuracy, either for shq.rt periods, as half an 

 hour, or for longer periods, as 8, 12 or more hours, in which latter case the appa- 

 ratus becomes a sort of integrating hygrometer, by which the total amount of 

 moisture in the air for a given period is indicated. 



Sketch of the Climate of Western India. 

 By Dr. Buist, LL.D,, F.R.S. L. 4' E. (^Communicated by Col. Sykes.) 



The author in this paper abstains from numerical details, and states as his reason 

 for doing so, that the " profuse employment of instruments occasions to a con- 

 siderable extent the more striking and obvious manifestations of the atmosphere to 

 be lost sight of, unless in so far as these are indicated by the barometer or thermo- 

 meter;" "and that picturesque and descriptive meteorology has almost altogether 

 been buried under minute instrumental details." He instances Dampier and Mount- 

 stewart Elphinstone as furnishing information of the kind he commends. 



He first notes that the European division of the year into four seasons, does not 

 hold good in Western India, where the year may be divided into two seasons only, 

 the rainy and the fair, the latter being divisible however into the cold and the hot*. 

 The monsoon sets in at Bombay with tremendous violence from the S.E. in the 

 beginning of June ; but the rains immediately go round to the S.W. and draw off 

 early in September. The winds blow throughout the year with the greatest regu- 

 larity. During the fair season, from October until May, there are alternating diurnal 

 and nocturnal winds, or land and sea breezes as they are called. The land wind 

 blows from easterly quarters, setting in after midnight and blowing until three or 

 four hours after sunrise, when a dead calm ensues. The sea breezes then blow from 

 westerly quarters. About the beginning of May the air becomes damp and muggy ; 

 the land and sea breezes become irregular, and a calm prevails over a great part of 

 the night, with the thermometer from 80° to 85°, and the air being surcharged with 

 moisture, people are debarred from sound sleep. About the middle of the month 



* Note hy Col. Sykes. — The Mahrattas divide the year into three natm-al seasons — the 

 Pawsalla (rainy), Hewalla (cold) and Oonalla (hot). 



