of a New Hygrometer. 35 



meter and Professor Daniell's as far as accurate calculation is 

 concerned, but as regards the degree of dryness on the ther- 

 mometric scale, or distance from saturation, it is undoubtedly 

 superior ; as in professor Daniell's instrument the two bulbs 

 are not under similar circumstances, for in the latter hygro- 

 meter the thermometer which indicates the temperature of 

 the air must be in the shade, and guarded from all the 

 sources of error to which it is liable, whereas, as I have 

 proved with respect to mine, those sources of error are of 

 less moment, precisely the same indications being given, 

 providing radiant caloric from surrounding objects be not 

 allowed to interfere. 



Sixth objection. That more time is required than could 

 be bestowed by an ordinary observer in order to make a 

 correct observation, as time must be allowed for the water 

 to acquire the temperature of the atmosphere. 



This objection is fully obviated by the method I have 

 adopted, namely, by keeping the ball constantly moist by 

 means of capillary attraction ; and no more time is re- 

 quired than would be necessary to make similar observa- 

 tions on two ordinary thermometers . 



Having answered every objection, I will for the present 

 stop here, and in my next paper state the view I take of 

 the manner in which the temperature of the moistened 

 bulb is reduced, and also the method to be adopted for 

 ' the purpose of obtaining the dew-point ; the mode of 

 comparing it with the hygrometer of Sir J. Leslie, and the 

 various uses to which it may be applied, both in meteoro- 

 logy and in different manufactures. 



I am, Sir, your obedient servant, 



John A. Mason. 



18, Claremont Place, Pentonvitle, 

 December 1st, 1835. 



{To be continued.) 



Article V. 

 Catalogue of Plants collected at Bombay. By 

 John Graham, Esq. 



We believe this to be- the first attempt at communicating 

 any information with regard to the botanical productions 

 of this beautifufpart of the western peninsula of Hindostan. 



d2 



