104 Professor Ren wick 071 f/ie 



way of making them comparable with the measures of foreign 

 nations. In confirmation of this opinion, 1 may urge the 

 examples of the French, the Danish, and the British govern- 

 ments, and that, still more recent, of Sweden. 



(3.) As to the mode of determining the unit of length in 

 relation to the standard existing in nature, and of deducing 

 thence the standard of weight, and of measures of capacity. 



I shall assume that the unit of lineal dimension that will be 

 adopted by the State, is the yard in common use on the day of 

 the declaration of independence, as prescribed in the law of 

 1784. This was, no doubt, identical with the British parlia- 

 mentary yard made in 1760. It luckily so happens, that we 

 possess the measure of the seconds pendulum made in the 

 buildings of this institution in reference to that very standard, 

 and consequently the means of making a yard that shall be 

 identical with the yard of the Revolution. For this purpose it 

 will be sufficient that the law should recognise that the standard 

 yard shall bear a certain proportion to that measure of the 

 pendulum. When the necessary experiments shall have been 

 made to determine the true length of this yard, its extremities 

 should be marked upon disks of an imperishable material, (gold 

 or platinum, for instance,) inserted at a proper distance in a 

 bar of brass, or rather of a more durable alloy of copper than 

 what, in ordinary language, is called by that name. The dis- 

 tance betAveen the two extremities of a bar is inadmissible in a 

 standard, in consequence of the alteration in length that is 

 caused by wear, as known in practice in the history of the yard 

 preserved in the British Exchequer. 



Such a bar will be subject to dilation and contraction by heat 

 and cold ; but the temperature at which its length is compared 

 with the pendulum should be given, and when it is to be com- 

 pared with, or its length transferred to, bars of the same mate- 

 rial, as both will be equally affected, no legal enactment is in 

 this case requisite ; but as measures in ordinary use are most 

 frequently of other materials, it will be necessary that the tem- 

 perature at which such comparisons must be made, or to which 

 they must be reduced by calculation, should be strictly speci- 

 fied. It would be proper to seek for this purpose a tempera- 



