Taylor.] 6b4: [Oct. 21, 



manner and at a certain temperature ; but that the standard be in no way 

 defined by reference to any natural basis, such as the length of the pendu- 

 lum vibratirxg seconds in a specified place. •■■ * * That the standard of 

 weiglit be defined by a certain piece of metal or other durable sub- 

 stance," etc. 



It thus appears as the result of this last commission in England, that the 

 people of that country are disposed to abandon all attempts at obtaining a 

 natural standard, and to recur to the authority of an arbitrary rod or piece 

 of metal, whose length has been derived from prescriptive custom. It should 

 be considered, however, that after a natural standard has been obtained, we 

 still have all the means of its material perpetuation, suggested in the com- 

 missioners' report. And no foreign community is ever likely to accept as an 

 authoritative unit of measure, a certain brass rod manufactured in England, 

 and incapable of any more precise definition. 



Mr. Baily was selected to prepare the new standard, having five copies of 

 the preceding on which to base his comparison ; on liis death, in 1844, Mr. 

 Sheepshanks continued the necessary observations. Of several standard 

 copies finally prepared by him, each being a square inch bar, of a bronze 

 consisting of copper with a small percentage of tin and zinc, 38 inches in 

 length, with half inch wells sunk to the middle of tlie bar, one inch from 

 •eacli end, in which the lines defining the yard are drawn on gold plugs — six 

 were finally selected and reported by the commissioners in March, 1854. Of 

 these, the one marked " Bronze 19 "^was selected as the parliamentary standard 

 yard, the remaining five" being deposited, along with copies of the standard of 

 weight, with as many public institutions and scientific bodies. These stand- 

 ards were legalized in July, 1855; and in case of loss of the parliamentary 

 €opy, it was provided that the standard should be restored by comparison of 

 the other selected copies, or such as might be available. 



Bronze bar No. 11 which has the standard length at a temperature of 61.79° 

 has been presented to the United States, and is the actual standard of com- 

 l^arison. 



In addition to the difficulties of obtaining from the pendulum the recon- 

 struction of a lost standard, as above indicated, it is not unimportant to note 

 that tliere is an original uncertainty in the determination of its length, of 

 nearly the thousandth part of an inch. " We cannot venture to say that the 

 clock's rate in a given day, can be determined certainly to within one-tenth 

 part of a second, although the comparisons have been made at an interval of 

 24 hours. Seeing then that the free pendulum is compared with the clock 

 only over a small fraction of the day, it is a great deal to expect that its daily 

 rate can be ascertained to within one second of time. A change of one 

 second per day in the I'ate of a clock, corresponds to a change of ^j^q, 

 in the length o| the pendulum, which is about ^J^ ^ of an inch, or Jg- of a 

 millimetre; and therefore we may regard this distance as indicating the 

 probable limit of exactitude" {Encyclopedia Britannica, 8th edition, Vol. 

 xvii, page 384, article "Pendulum," by Edward Sang). 



Note D. 

 The only account we have been able to obtain of the important movement 

 of Charles XII toward superseding tlie decimal by the octonary system, 

 throughout Sweden, is that contained in a volume entitled " A Compendium 



