Daniell on a new Hygrometer, 131 



tondense en liquide qu*on observe dans le cas cite." ^ Now, I 

 tnust confess, that the expression which I have adopted, (al- 

 thougli I am far from wishing to maintain that it is the very 

 best that might have been selected,) appears to me at least as 

 correct as that which my critics propose to substitute; for, con- 

 sidering that it is but a mathematical line which divides the 

 point at which vapour begins to exist, from the point at which 

 it begins to condense, he must have microscopic eyes indeed 

 thatcan discern the division; and supposing the " temperature 

 destructive de la vapeur," to be accurately represented by 

 60° of the thermometric scale, he will be an accurate mathe- 

 matician indeed who will represent the " temperature consti- 

 tuaiite" by any nearer sign. 



And now, expressing my acknowledgments to the Genevese 

 philosophers for their admission of my new instrument, ** peut 

 fournir au physician qui le poss^de, le desir et les moyens de 

 I'employer, tant k la demonstration des principaux phenom^nes 

 de Tevaporation, qu'^ I'etude plus approfondie des singuli^res 

 et importantes modifications de la vapeur aqueuse, consideree 

 dans I'air et dans le vide," I shall proceed to contribute 

 my endeavours for the accomplishment of this desirable 

 purpose. 



The annexed Table shows at one view the principal results 

 of the twelve-month's experiments, divided for the facility of 

 comparison into periods of half-years, quarters, and half- 

 quarters. It will be easily understood from inspection, and 

 will require but little explanation. The means of the different 

 periods are represented by the larger figures, and the extremes 

 by the smaller, shewing the range of the several instruments in 

 the respective intervals. 



It may be observed, that the barometric results of the first 

 quarter do not exactly correspond with those already pul- 

 lished in the Journal. This is owing to a correction which I 

 have applied in consequence of a defect in the first barometer 

 which I employed. I have since made use of a very excel- 

 lent instrument of large dimensions of the syphon form, with 

 which I compare all others that I have occasion to employ. 



K 2 



