Memoir of' the late Francis Baily, Esq.^ F.R.S., S^c. 59 



of some communications on the subject between Mr. Baily, 

 Mr. Bethune, and the Astronomer Royal, the latter was in- 

 duced to draw the attention of Government to the subject, an 

 occasion having arisen which rendered the mention in an offi- 

 cial form unavoidable. And on the lUhof May of the same 

 year a commission was appointed, consisting of seven* mem- 

 bers (Mr. Baily being one), to report on the course most ad- 

 visable to be pursued under these circumstances. To this 

 duty, which involved the hearing of a vast deal of evidence and 

 much personal attendance, Mr. Baily gave his unceasing at- 

 tention ; suggesting many valuable points, both practical and 

 theoretical ; and, on the Report of the Commission being 

 agreed on, and the practical formation of new standards, in 

 conformity with the view therein taken of the. subject, being 

 referred by Government to the same commissioners, Mr. Baily 

 undertook, to the general satisfaction of the whole body, and 

 at their particular request, the delicate and important task of 

 reconstructing the standard of length — a task which, unhap- 

 pily, he did not live to complete. On whomsoever may de- 

 volve the completion of this standard, it will be satisfactory to 

 the members of this Society to know that, among the evidence 

 adduced for its restoration, the scale prepared for it by Mr. 

 Baily necessarily forms a most important and prominent 

 feature. 



Density of the Earth. — The accurate determination of one 

 fundamental quantity naturally leads to inquiry into others. 

 To make our globe the basis of measurement for the dimen- 

 sions of the planetary system and of the visible universe, its 

 form and magnitude must first be accurately known. To 

 make it afford a scale by which the masses and attractive forces 

 of the sun and planets can be expressed in terms conveying a 

 j)ositive meaning, its density must be ascertained, as compared 

 with that of substances which occur on its surface, with which 

 our experience is familiar, and from which our notions of ma- 

 terial existence are drawn. The fine experiment of Caven- 

 dish, confirmed as it was, in its general result, by the opera- 

 tions on Schehallien, had satisfactorily demonstrated the con- 

 tinuity of the Newtonian law of gravity, from such vast di- 

 stances as astronomy is conversant with, through the inter- 

 mediate steps of the diameters of the earth, and of a mountain, 

 down to those minute intervals which intervene between the 

 parts of a philosophical apparatus, and their agreement within 

 as moderate limits as could have reasonably been expected, 

 had even led to something like a probable estimate of the 

 earth's density, which, however, could never be regarded as 

 * An eighth was subsequently added. 



