Royal Society. 221 



deviate from the course which had previously been ahvavs pursued 

 by mathematicians, and to employ equations in which the true lon- 

 gitude is the independent variable. Instead, however, of integrating 

 the equations of motion by the method of indeterminate coefficients, 

 as the author had proposed, M. Poisson recommends the adoption of 

 the method of the variation of the elliptic constants. In the present 

 paper, Mr. Lubbock states the reasons which have determined him 

 not to employ the latter method, founded chiefly on the advantages 

 of obtaining complete uniformity in the methods used in the theories 

 of the moon and of the planets, and also in that of a greater rapidity 

 of approximation by the improvements introduced in these methods. 



Laplace, in the Mecanique Celeste, alludes to an equation of long 

 period, of which the argument is twice the longitude of the moon's 

 node, plus the longitude of her perigee, minus three times the longi- 

 tude of the sun's perigee ; and M. Poisson has shown that the co- 

 efficient of the corresponding argument in the development of the 

 disturbing function equals zero : but the author shows that the same 

 result may be arrived at very simply, by means of the method of de- 

 veloping the variation of the disturbing function. 



Dec. 19. — " On the Quantity and Quality of the Gases disengaged 

 from the Thermal Spring which supplies the King's Bath, in the City 

 of Bath." By Charles G. B. Daubeny, M.D., F.R.S., Professor of 

 Chemistry in the University of Oxford. 



The author, pursuant to an intention expressed in a former paper 

 read to the Society, undertook a series of experiments, for the purpose 

 of measuring the gas evolved from the thermal springs at Bath during 

 a period of time sufficiently long to enable him to determine with 

 tolerable precision its average amount, and to ascertain whether 

 any great diurnal variations in its quantity can be detected. He 

 also kept during the same period a corresponding register of the 

 conditions of the atmosphere, as to temperature, humidity and 

 pressure, in order to learn whether any connexion could be traced 

 between these conditions and the quantities of gas evolved. The 

 supplies, both of water and of gas, from the hot bath and the Cross 

 bath being insignificant compared with those from the King's bath, 

 the author confined his inquiries to the. last of these, and chiefly to 

 the gas arising from the apertures within its central area, which is 

 about twenty feet in diameter ; the other apertures without this circle 

 from which gas issued being carefully stopped up. The gas was col- 

 lected by a funnel-shaped apparatus, constructed of several sheets of 

 iron riveted together, and the seams rendered airtight by white lead, 

 supported on a frame, with contrivances for raising and lowering it as 

 occasion might require. The observations were made (luring periods 

 of from five to fifteen minutes, and continued daily from the I 7th of Sep- 

 icmluT to the 18th of October inclusive. The average quantity of gas 

 evolved per minute, as deduced from the mean of all" the observations, 

 is 267 cubic inches, giving a total daily volume of 223 cubic feet. 



The author, by referring to the accounts on record of other thermal 

 w iters, concludes that the evolution of gas is a phenomenon as in- 

 timately connected with thtf constitution of these waters, as tin' pre- 

 sence of a definite quantity of certain saline ingredients, or the pos- 



