50 J. M. Balihvln: 



made to this in the Committee's report ; presumably it was cast 

 shortly before the other bars. This bar is in good preservation 

 and the lines on the plugs are very good. 



There is also at the Melbourne Observatory a second standard 

 yard of similar metal and of the same length and cross section. 

 The cylindrical holes are J-inch in diameter, and only 0.1 inch 

 deep, with gold plugs as before, but the lines parallel to the axis 

 are -J-inch apart. The lines are not good, the central one on one 

 plug being distinctly curved, and on the other not of uniform 

 width. This bar was constructed in 1864, and is marked as 

 standard at 57° Faht. The certificate issued by the Exchequer 

 is dated 4th June, 1866. The bar will be referred to as (1383). 



The expansion of 36 inches of the bronze used is given by 

 Airy as 0.000341 ins. per degree Fahr. (I.e., p. 681), so that, as- 

 suming the permanence of the bars, the original comparisons 

 would give (40) — (1383)= —.00170 inches when the bars are 

 the same temperature. In August, 1915, these two bars were 

 compared, and preliminary measures showed that (40) — (1383) 

 = -t-.002 inches. . At this time the history of (40) was unknown 

 to me, but the workmanship gave evidence that it had been pre- 

 pared with much greater care than (1383). The temperature 

 at which the bars were standard was given . in the one case as 

 61.99° F., in the other as 57° F. This pointed to the work of 

 comparison of (40) having been more accurately carried out. 

 The difference between the original and the later comparisons 

 was so marked that it w^as impossible from the evidence before 

 mxC to have any certainty of what the standard yard really was, 

 and it was impossible at that time to send one of the bars to 

 England to be re-investigated. In this difficulty, inquiries were 

 made of the Deputy Warden of the Standards as to the history 

 of bar (40), but before the receipt of his reply, it was identified 

 by means of the paper cited above as being one of the original 

 forty standard yard bars, and it was found that similar standards 

 had been sent to Sydney and to Hobart. Further enquiries 

 showed that these standards were still in existence, and thus 

 a way was opened for an accurate determination of the yard 

 by means of an intercomparison of these three original bars, 

 each a replica of the British Imperial Standard Yard bar. After 

 considerable delay, I was authorised by the Victorian Govern- 

 ment to arrange for this intercomparison, and through the 

 courtesy of the Minister for Lands of New South Wales, and 



