104; Mr. Ivory's Observations on Mr. Meikle's Reply, 8)-c. 



pendulum (as I presume it will be) should ever be re-measured 

 and re-swung with a view to obtain a more correct and per- 

 manent comparison for a standard measure ; for, in a national 

 work, no labour or expense ought to be spared, in order to 

 obtain the greatest possible accuracy. 



I ought not to omit mentioning that the two convertible 

 pendulums (the one of iron, and the other of copper) belong- 

 ing to the Astronomical Society, and now in the care of Cap- 

 tain Foster, in his voyage of experiment and discovery, are 

 formed on precisely the same plan, as the pendulum alluded to 

 in the first part of this communication. I had not an oppor- 

 tunity of measuring the distances between the knife edges, 

 previous to his departure: but, on his return, it will be in- 

 teresting to ascertain whether those pendulums indicate ano- 

 malies similar to those which have been the subject of this 

 communication. 



January 20, 18^9. FllANCIS Baily. 



XV. Some Observations on Mr. Meikle's Iteply, fublished in 

 the last 'Number of the Qiiarterly Journal of Science. By 

 James Ivory, Esq. M.A. F.R.S. ^c* 



IV/rR. MEIKLE seems resolutely bent on effecting the 

 ■^^■^ thorough reforin, and on weeding out every blemish from 

 mathematical science. For my part, I am fully resolved to 

 oppose no obstacle to the accomplishment of so laudable a 

 project. On the contrary he may reckon upon it as a thing 

 not doubtful, that I shall approve and adopt every improve- 

 ment he may be able to establish on good grounds. 



He is no less bent on giving to what he calls my formula 

 any shape, and on making any use of it, he pleases. There 

 seems, however, to be some misgiving on this point; for, in a 

 note, he calls upon his readers to recollect what the formula 

 is. On the other hand, I call upon them to go back to the 

 princijjles from which the formula is deduced, this being the 

 best way to judge of its import and to guide in its right ap- 

 plication. 



In this Journal for February 1827, p. 94, I have arrived at 

 this conclusion : 



" The heat extricated from air when it undergoes a given 

 condensation, is equal to ^ of the diminution of temperature 

 required to produce the same condensation, the pressure being 

 constant." 



And as the same quantity of heat, which is evolved by a 



* Communicated by the Author. 



given 



