362 Mr, PowelPs Appendix to M, Ramond*s Instructions [Nov, 

 squares, and confining ourselves to the first powers of — , and 



or-. 



a 



120 



The first factor 1 may be reduced into numbers taking 



a =6366198 m. as we before assumed ; it diminishes the baro- 



M 



A Si 



metric coefficient by 0'35 m. which gives - — = 18334-11 m. 



(1 



+ ?r'^ 



This coefficient differs very little from that adopted by M. Ra* 

 mond, viz. 18336 m. : this he deduces in his first memoir ; it 



= 60158-7 feet, but the variable multiplier (l + — ) does not 



appear in his formula. If in Biot's we take a mean value of (r) 

 at 400 m. since any value of r must be very small compared with 

 a, and substituting for (a) its value, the fraction will continue 

 very small, and we shall have 18334-11 x 1 + -00012 nearly, 

 which gives 18336*3 for the constant coefficient. 



II. The publication of M. Kamond from which I have given 

 the foreooing abstract, comprises in the first place four memoirs 

 of the highest interest discussing various points connected with 

 the subject of barometric observations. These are followed by a 

 second part, entitled, " Elementary and Practical Instructions 

 for the Application of the Barometer to the Measurement of 

 Heights." It is this part of the work which I have here 

 abridged, and which may be considered as in some degree 

 bringing together the results of experiments detailed in the 

 preceding memoirs. Those relating to practical directions for 

 observing appear to me sufficiently detailed in the "Instructions;" 

 but one or two points connected with the formula, and discussed 

 in the first memoir, may, I conceive, be here properly introduced 

 to the more particular attention of the reader. 



In his first Memoir, Part I. M. Ramond has given the results 

 of barometrical measurements, which have shown him the 

 necessity of augmenting the constant coefficient adopted by 

 M.Laplace 17972-1 m. bv rather less than l-42d, so that it 

 becomes 18393 m. or in feet 60345. He gives the measured 

 height of four mountains, which he compares with the height 

 convputed by the several formulae of Laplace (with the new 

 coefficient), Trembley, Kirwan, Shuckburgh, and Roy (coeffi- 

 cient 184-4), the first being constantly found the most preferable. 

 " As the ultimate result," he says (p. 11), " in eight observa- 

 tions, made with peculiar care, the formula of M.- Laplace, with 

 the new coefficient, has been correct five times, and that of 

 Trembley only twice. Now in these eight observations the 

 mean temperature varied from 8-375° to 19*53°, and we are in 



