3S0 Observations ofi the Hygrometer. 



had a notable example in the parliamentary offer of a reward for 

 a perpetual motion, — a reward, the hope of receiving which, has 

 led many ingenious men to ruin. The last approaches as near- 

 ly as possible to the natural state of things, where a meritorious 

 action works out its own reward. We have resolved on an amal- 

 gamation of the two, so as to combine all the advantages, but 

 all the disadvantages too, of both. This course will be attended 

 with one important result, that in a few years our own records 

 will furnish us with data wherefrom to draw a decision ; it will 

 then be proper to return to this important subject. 



That encouragement, however, which we can give aggregate- 

 ly is trifling in comparison with that which flows from our in- 

 dividual exertions. It is in the power of each to recommend a 

 better article, or a more commodious instrument; and even 

 though the newer commodity be a little more expensive than 

 the old, it is the duty of every one to give the improved process 

 a fair chance, in order to accelerate, as much as possible, the 

 yet remote maturity of the human race. 



Sept 4. 1834. Edward Sang. 



Observations on the Hygrometer. 



In a former paper *, a sketch was attempted of the theories 

 which have been proposed of the Hygrometer by evaporation ; 

 and a modification of Sir John Leslie's formula for finding the 

 dew-point was suggested. 



The writer is gratified to find, that one so familiar with the 

 subject of that communication as Mr H. Meikle, has expressed 

 a favourable opinion of the Table of Dew-points which it con- 

 tains "I". With respect to some of the errors which that gentle- 

 man has pointed out, they are readily acknowledged ; especially 

 that of supposing a given volume of air, of given temperature, 

 to require more water for its saturation under a great, than un- 

 der a small pressure. 



Mr Meikle, in the same paper, explains a mode, which he has 

 discovered, of expressing geometrically the relation between 

 • Edinburgh New Philosophical Journal, vol. xv. p. 273. 

 -j- Ibid. vol. xviL p. 98. 



