liO CATALOGUE. — ^PHILOSOPHY AND ARTS, PRACTICAL MECHANICS. 



ih order to measure the fraction, expressing the distance of 

 the other microscope from another division. 



The comparison was repeated in the same manner the 

 4th Brumaira (aOth October) last, at the house of one of 

 the committee, and after several experiments, agreeing very 

 satisfactorily with each other, it was found that at the tem- 

 perature 12.75°', or 55° of Fahrenheit, the standard of 

 platina was 39.378I, and that of iron 39.3795 English 

 inches. 



The two metres being intended to be equal at the tem- 

 perature of melting ice, these operations may be verified by 

 reducing their results to that temperature. For this deter- 

 mination we are provided with the accurate exiitriments 

 made by Borda, and the committee of weights and mea- 

 sures, on the dilatation of platina, brass, and iron ; from 

 which it appears, that for every degree of the decimal tlicr- 

 mometer, platina expands .00000856; iron .00001156; 

 and brass .00001783 ; for Fahrenheit's scale these quanti- 

 ties become 476,642, and 990 parts in a hundred millions. 

 From these data we find, that, at the freezing point, the 

 standard metre of platina was equal to 39.38280, and that 

 of iron to 39-38265 English inchesof M. Pictet's scale. The 

 difference is less than the 500thof a line, 'or the 200000th 

 of the whole metre, and is therefore wholly inconsiderable. 



The result of the whole comparison is therefore this. 

 Supposing all the measures at the temperature of melting 

 ice, each of the standard metres is equal to the loooooooth 

 part of the quadrant of the meridian, and to 39-38272 Eng- 

 lish inchesof M. Pictet's scale. Paris, 16. Jan. IB02. 



On examining the reduction of the standards of platina 

 and iron to the freezing point, it appears that they differ 

 somewhat less than is stated in the report, and that they 

 coincide within a unit in the last place of the decimals 

 expressing their magnitudes, or one ten thousandth of an 

 inch. The standard of platina at ^e freezing point be- 

 comes equal to 39.373SO, and that of iron to 39.37370 

 English inches on the scale of brass at 55°, and the mean 

 of these to 39.37100 English inches at 62°, which is the 

 temperature that has been universally employed in the 

 comparison of British standards, and in the late trigoi ome- 

 trical operations in paiticular. This result agrees surprisingly 

 with Mr. Bird's determination of the lengths of the toiscs 

 sent by Mr. Lalandc to Dr. Maskelyne, of which the mean 

 ■was 76.734 inches : hence the metre, having been found to 

 contain 36.9413 French inches, appears to be equal to 

 39.3702 English inches: or rather to be either 39.3694 or 

 39.3710, accordingly as the one or the other of the two 

 toises happens to have been the more correct ; we may 

 therefore give the preference to that which measured 76.738 

 Inches. 



Allowing the accuracy of the French measurements of 

 the arc of the meridian, the whole circumference of the 

 globe will be 24S55.43 English miles, and its mean diame- 

 ter 7911.73. Joum, R. I., I. 129. 



In tlie Bibliotheque Britannique, Vol. 19, No. 4. we 

 find a description of the comparer of Lenoir, by Mr. Prony. 

 Its peculiarity consists in the application of a bent lever, 

 of which the shorter arm is pressed against the end of the 

 substance to be measured, while the longer serves as an 

 index, carrying a vernier, and pointing out on a graduated 

 arch the divisions of a scale, which by this contrivance is 

 considerably extended in magnitude. It does not, however, 

 at first sight, appear to be certain that the difficulty of fix- 

 ing the a.tis of the lever with perfect accuracy, and of form- 

 ing a curve for the surface of the shorter arm, or of reducing 

 the graduation of the arc to equal parts of the right line in 

 the direction of the substance to be measured, might not 

 in practice more than counterbalance the advantage of this ^ 

 mechanical amplification of the scale, over the simpler 

 optical method employed in the English instruments. 

 Journ. R. I., I. 180. 



By an act of Oueen Anne, the wine gallon is fixed at 

 231 cubic inches. 



Hence, A pint is 28.87-5 cubic inches. 



A quart 57-73 



A barrel 7276.5 

 A hogshead 14553. 



A pint, beer measure, ale measure, and 

 country measure, is 35-25 cubic inches. 



