FISCHER: LENGTH STANDARDS AND MEASUREMENTS 149 



was supposed to be equal to Bird's yard, served as the standard 

 for the United States until 1856. 



On October 16, 1834 the Imperial standard (Bird's standard 

 of 1760) was destroyed by the burnmg of the House of Parlia- 

 ment, and very soon thereafter steps were taken to recover its 

 length; but it was not until 1855 that the new Imperial standards 

 were completed and accepted by Parliament. 



Turning now to the French standards of length, there is evi- 

 dence that the earliest of these, the Toise of Paris, goes back 

 to the time of Charlemagne (742-814). It is stated that: 



in 1668 the ancient toise was reformed by shortening it five lines (about 

 one-half inch), but whether this reformation was an arbitrary change, 

 or merely a change to remedy the effects of long use, is not known. 

 The old bar was made of iron with the two ends turned up at right 

 angles so as to form a matrix, and the testing of end measures was 

 effected by fitting them between the bent ends. Being placed on the 

 outside of some public building, it was exposed to wear from constant 

 use, to rust, and even to intentional injur3' by malicious persons. 



The earliest use of the toise for scientific purposes was' by 

 Picard and Cassini in their measurement of a degree of the me- 

 ridian passing through Paris. This toise was made in 1668 and 

 would, no doubt, have become the scientific standard of France 

 if it had not disappeared. The second toise used for scientific 

 purposes was one used in the measurement of the Peruvian Arc. 

 This bar, which is known as the Toise du Perou and made m 

 1735, was made the legal standard of France by an order of Louis 

 XV, dated May 16, 1766, and is still preserved at the Observatoire 

 at Paris. 



As is well known, the meter was intended to be equal to the 

 ten millionth part of the quadrant of the terrestrial meridian; 

 but that the measurements of the arc upon which it was based 

 were referred to the toise is a fact of less common knowledge. 

 The measurement of the meridian was entrusted to Mechain and 

 Delambre by the French Academy of Sciences, who carried it 

 on during seven years from 1791 to 1798. The unit of length 

 used by them was the Toise du Perou, and from the arc of 9°40'45" 

 actually measured, they inferred the length of an arc of the 



