ON DRAWING, WRITING, AND MEASURING. 35 



have suspended its introduction for the present. We may, however, 

 expect that it will ultimately be brought into general use." 



Such is Mr. Laplace's account of the new system of measures, the result 

 of the joint labours of many of the ablest mathematicians on the continent. 

 There is not at present any great probability that it will ever be employed 

 in this country. It is of little consequence from what the original unit has 

 been derived, unless we can with ease and accuracy recur to its origin : 

 and whether a standard has been first adjusted according to the circum- 

 ference of the globe, or to the foot of an individual hero, the facility of 

 comparing other measures with it is the same. It is confessed that the 

 pendulum affords the readiest method of recovering the standard when 

 lost ; and if it was necessary for the Committee of the French Academy 

 to determine a unit absolutely new, it would perhaps have been more 

 eligible to fix on one which was independent of any ulterior comparison, 

 than to seek for an ideal perfection in attempting to copy from a more 

 magnificent original ; to say nothing of the uncertainty with regard to the 

 ellipticity of the earth, and the probable irregularity of its form in various 

 respects. On the other hand, it must be allowed, that the correct deter- 

 mination of the length of the pendulum has sometimes been found more 

 difficult than Mr. Laplace's statement would lead us to suppose it, and we 

 cannot depend on any measurement of it as totally exempt from an error 

 of the ten thousandth part of the whole. 



The metre, as definitively established by the government of France, is 

 equal to 39-nyVV English inches, measured, as it has been usual in this 

 country, on a standard scale of brass, at the temperature of 62 of Fah- 

 renheit; while the French, on the contrary, reduce the length of their 

 measures to that which they would acquire at the freezing point. Hence 

 ten thousand inches are nearly 254 metres, a thousand feet 305 metres. 

 The length of the pendulum vibrating seconds in London, was found by 

 George Graham, from a mean of several experiments, all agreeing very 

 nearly together, to be 39-rVo- inches. This is also nearly a mean between 

 the length which may be deduced, with proper corrections, from Borda's 

 experiments at Paris,* and Mr. Whitehurst's experiments made in Lon- 

 don, t with the apparatus invented by Mr. Hatton,;}; where the length 

 ascertained is the difference between the lengths of two pendulums vibrat- 

 ing in different times. Mr. Whitehurst's measures, however, require some 

 corrections, which Mr. Nicholson has pointed out. The fall of a heavy 

 body in the first second appears, from this determination of the length of 

 the pendulum, to be sixteen feet one inch and a tenth. 



Of the old French measure, 15 inches made nearly 16 English, and 76, 

 very exactly 81 ; the toise was 76 T % 3 A inches. In Germany the Rhinland 

 foot is generally used ; 100 of these feet make 103 English. 



A wine gallon contains 231 cubic inches ; an ale gallon is the content of 

 10 yards of a cylindrical inch pipe. 



^ See Base du Systeme Metrique, vol. iii. 



f Whitehurst's Attempt to obtain Measures of Length from the Measurement of 



Time, 4to, Lond. 1787. Do. on Pendulums, 1792. 



I Hatton's Machine for finding a Standard. Trans, of the Soc. of Arts, I. 238. 



