Dimensional Properties of Matter in the Gaseous State. 335 



proposition of Gen. Schubert we think it undesirable to pass in 

 complete silence over one point, which, though it does not 

 belong directly to the subject, yet to avoid misunderstanding 

 demands some explanation. We refer to the statement, fre- 

 quently occurring both in General Schubert's essay in the 

 Astronomische JSachrichten and in his communication to the 

 Academy, that it is to Airy that the English arc owes its pre- 

 eminent position as marking an epoch in geodesy, through 

 the application by him of the before-mentioned corrections to 

 individual latitudes. This statement seems to be entirely 

 without foundation ; for in the account of the English arc we 

 find nothing which can be regarded as in favour of this state- 

 ment, but rather the contrary. The only occasion on which 

 Airy's name occurs in that work in connection with the in- 

 vestigations of local attraction is in the mention of his 

 ingenious speculation by which he seeks to explain the pheno- 

 menon that the Himalayas exert no sensible influence upon 

 the plumb-line at the neighbouring stations of the Indian arc. 

 This speculation alone should have sufficed, to prove that Airy 

 did not approve of the application generally and unconditionally 

 of such corrections. I have moreover had the opportunity, 

 partly by letter and partly by oral communication, of learning 

 what are Airy's views on this point ; and think myself entitled 

 to say that that distinguished philosopher is in agreement with 

 me in the opinion that such correction of latitudes in general 

 must be regarded as opposed to the geodetical purpose, while 

 at the same time he certainly does not ignore the bearing which 

 such investigations must have upon geological studies. If 

 there is any thing in the said English work which could 

 suggest the thought that Airy was directly concerned in it, 

 it would be the careful, circumspect, and, in a word, mas- 

 terly treatment of the geodetic material ; but for the credit of 

 this too, Airy, as I know from his own lips, waives all claim : 

 it belongs exclusively to the authors named upon the title-page 

 — to the present Director of the Ordnance Survey, Sir Henry 

 James, and to his distinguished Assistant, Captain Clarke. 



XLYI. Certain Dimensional Properties of Matter in the Gaseous 

 State. An Answer to Mr. George Francis Fitzgerald. By 

 Professor Osbobxe Reynolds, F.R.S.* 



IN the February number of the Philosophical Magazine 

 there appeared a paper by Mr. Fitzgerald, in which 

 he criticised my paper " On certain Dimensional Properties 

 of Matter in the Gaseous State," Philosophical Transactions 

 * Communicated by the Author. 



