97 



phry does not admit of this conclusion. The author has adopted 

 throughout the calculations in this paper the supposition that the 

 hydrogen in water is as 2 to 15 to the oxygen ; and consequently, 

 he says, has taken the number 15 to represent the latter element. 

 If the hypophosphorous acid be regarded as a simple compound of 

 oxygen and phosphorus, it will consist of 45 phosphorus +15 oxy- 

 gen ; phosphorous acid of 45 phosphorus -+ 30 oxygen ; phosphoric 

 acid of 45 phosphorus + 60 oxygen. 



Sir Humphry concludes this paper with some incidental observa- 

 tions relating to the compounds of phosphorus. 



New Experimental Researches on some of the leading Doctrines of Ca- 

 loric ; particularly on the Relation between the Elasticity, Tempera- 

 ture, and latent Heat of different Vapours ; and on Thermometric 

 Admeasurement and Capacity. By Andrew Ure, M.D. Communi- 

 cated by W. H. Wollaston, M.D. F.R.S. Read April 30, 1818. 

 [Phil. Trans. 1818,^. 338.] 



This paper is divided into three sections. In the first the author, 

 after taking an historical view of the different experiments under- 

 taken by Robinson, Watt, Dalton, Biot, and some others, relating 

 to the elastic force of vapours arising from different bodies at dif- 

 ferent temperatures, and after pointing out the sources of error and 

 imperfection to which they are liable, proceeds to describe the ap- 

 paratus which he employed, which is further illustrated by an an- 

 nexed drawing. The space which contains the vapour for experiment 

 is about half an inch of a barometer tube, against which the oblong 

 bulb of a delicate thermometer rests so as to indicate the true tem- 

 perature. The contrivance is such, that though the liquid and in- 

 cumbent vapour are restricted to the summit of the tube, its pro- 

 gressive range of elasticity may be measured from to 200 above 

 the boiling point of water, or from an elasticity of - 07 inch to that 

 capable of sustaining 36 feet of mercury, without heating the mer- 

 curial column itself. In this section of the paper are several tables 

 of results, showing the elastic force of the vapour of water in inches 

 of mercury, at temperatures between 24 and 312 ; and also that of 

 alcohol, ether, oil of turpentine, and naphtha. The second section of 

 Dr. Ure's paper relates to thermometric admeasurement, and to the 

 doctrine of capacity. He does not consider the thermometer liable 

 to the uncertainties which are supposed to belong to it by Mr. Dal- 

 ton, but that it is an equable measure of heat, in consequence of its 

 possessing an increasing rate of expansion, and which is compensated 

 for by a quantity of the quicksilver getting out of the bulb into the 

 tube, and consequently out of the action of the heat, the bulb being 

 the only part heated in all ordinary cases. 



In the third section, relating to the latent heat of different vapours, 

 Dr. Ure details experiments made to ascertain the caloric existing in 

 different vapours, and the .temperatures at \vhich they respectively 

 acquire the same elastic force. 



VOL. II. H 



