Mr. C. K. Akin on the Compressibility of Gases. 289 



The accompanying sketch map (Plate V.) will enable the argu- 

 ments that I have attempted to adduce to be followed more readily, 

 and the conclusions I have drawn from them to be seen at a glance; 

 and in it I have traced the conjectural outline of the Charento- 

 Pyrenean basin. 



XL. Note on the Compressibility of Gai 

 By C. K. Akin, Esq.* 



IN the following paper will be proposed a few remarks, made 

 some considerable time ago, the gist or moot point of which 

 is to be the degree of numerical accuracy belonging to the several 

 formulae which have been computed by M. Regnault in the latter 

 part of his celebrated memoir on the law of Boyle (or Mariotte), 

 from the experimental data contained in the early partf — the pur- 

 pose which these formulae are to serve being to supplement or (if 

 properly written) to supersede provisionally the Boylean formula 

 to a certain extent, until the complete law of gaseous compressi- 

 bility shall have been theoretically or otherwise determined. The 

 importance of the formulae referred to being obvious, the necessity 

 of evaluating the several constants which they imply with all pos- 

 sible rigour, or with so much, at least, as the nature of the 

 experimental groundwork upon which the formulae rest will not 

 render futile to attempt, will be no less evident. And if the 

 actual deduction of the constants supplied should, as really ap- 

 pears to the present writer, not fulfil the requirement specified, 

 within limits at once attainable and intended to be attained by 

 the computer, the obligation to direct attention to the matter 

 could not well be avoided, and is in this case the more easy to 

 comply with, as the means of remedying the observed short- 

 comings may be readily pointed out. 



1. The first of the remarks to be submitted involves, as a ne- 

 cessity, some preliminary statements as to the proper mode of 

 applying the law of Boyle in certain very common instances. If 

 there be nothing namely to object to in the ordinary definition 

 of this law, as the postulate requiring the direct proportionality 

 of pressures and densities, or the inverse proportionality of pres- 

 sures and volumes, in gases when at a constant temperature, so 

 far as it goes, it must still be observed to stand in need of some 

 special help to interpretation, in the case of gaseous masses the 

 volumes encompassed by which are finite in regard of vertical 

 extent. Or rather, whenever it is expedient to apply the law in 



* Communicated by the Author. 



f See " Memoire sur la Compressibilite des Fluides elastiques," Me'moires 

 de I'Academie des Sciences, vol. xxi. p. 32.9. 



Phil. Mag. S. 4. Vol. 25. No. 168. April 1863, U 



