42 Dr Davy's Remarks on the Claims to the 



that part of the scale the whole pressure becomes of the 

 order of errors of observation. 



In conclusion, it appears to me that the following proposi- 

 tion, to which I have been led by the theoretical researches 

 referred to at the commencement of this paper, is borne out 

 by all the experiments I have quoted, especially by those of 

 greatest accuracy, and may be safely and usefully applied to 

 practice. 



If the maximum elasticity of any vapour in contact with its 

 liquid be ascertained for three points on the scale of the air- 

 thermometer, then the constants of an equation of the for m 



Lor.p=„_^_2: 

 t fi 



may be determined, which equation will give, for that vapour, 

 with an accuracy limited only by the errors of observation, the 

 relation between the temperature [t), measured from the absolute 

 zero (2746 centiyrade degrees below the freezing point of water), 

 and the maximum elasticity (P), at all temperatures between 

 those three points, and for a considerable range beyond them. 



Some Hemarks on the Claims to the Discovery of the Composi- 

 tion of Water. By JoHN Davy, M.D., F.R.S., Lond. and 

 Edin., Inspector- General of Army Hospitals, &c. (Com- 

 municated by the Author.) 



In editing the collected works of my brother Sir H. Davy, 

 I had occasion to make some observations on the above sub- 

 ject, which, at that time (1839), had a good deal of attention 

 given to it, in consequence of the claims then brought for- 

 ward by the friends of Mr Watt, in favour of the merit of 

 the discovery of the composition of water being due to him 

 alone, to the disparagement of Mr Cavendish, whom the 

 most zealous of those friends evidently wished to exhibit as 

 a plagiarist, or as having derived the idea of the composition 

 of water from Mr "Watt, without acknowledgment. 



In a work, published in 1846, by J. P. Muirhead, Esq., 

 entitled, " Correspondence of the late James Watt, on his 

 Discovery of the Theory of the Composition o i Water," this 



