On the Maximum Density of Water. 41 



from perturbations the unknown place of the disturbing body 

 was first solved here; that the planet was here first sought 

 for; that places of it were here first recorded; and that ap- 

 proximate elements of its orbit were here first deduced from 

 observation. And that all this may be said is entirely due to 

 the talents and labours of one individual among us, who has 

 at once done honour to the University and maintained the 

 scientific reputation of the country. It is to be regretted that 

 Mr. Adams was more intent upon bringing his calculations to 

 perfection, than on establishing his claims to priority by early 

 publication. Some may be of opinion, that in placing before 

 the first astronomer of the kingdom results which showed that 

 he had completed the solution of the problem, and by which 

 he was, in a manner, pledged to the production of his calcu- 

 lations, there was as much publication as was justifiable on the 

 part of a mathematician whose name was not yet before the 

 world, the theory being one by which it was possible the prac- 

 tical astronomer might be misled. Now that success has 

 attended a different course, this will probably not be the ge- 

 neral opinion. I should consider myself to be hardly doing 

 justice to Mr. Adams, if I did not take this opportunity of 

 stating, from tlie means I have had of judging, that it was 

 impossible for any one to have comprehended more fully and 

 clearly all the parts of this intricate problem ; that he care- 

 fully considered all that was necessary for its exact solution ; 

 and that he had a firm conviction, from the results of his cal- 

 culations, that a planet was to be found. 



XI. On the Maximum Density of Water. 

 By James P. Joule, Esq. and Dr. Lyon Playfair*. 



IN all researches on specific gravity the selection of a pro- 

 per standard of comparison is a matter of great importance. 

 For obvious reasons water has been universally selected as 

 this standard ; but a diversity of opinion has been enter- 

 tained as to the temperature at which the gravity of water 

 should be called unity. Hence, whilst our continental neigh- 

 bours have adopted the freezing temperature, our own coun- 

 trymen have generally chosen the temperature of 60° Fahr. 

 Water at 60° cannot be a desirable standard, on account of 

 its high rate of expansion at that temperature ; and for the 

 same and other reasons the temperature of 32° is not at all 

 more convenient. We conceive that it would be much more 

 philosophical, and lead to many practical advantages, if water 



• Communicated by the Chemical Society: having been read April 20. 

 1846. .- o J . 



