OF ARTS AND SCIENCES. 307 



(b.) That the meters of the Royal Society do not admit of exact 

 measurements in their present state. 



(c.) That Kater has himself declared his own determination to be 

 erroneous. 



(d.) That the values given by Baily are expressed in terms of the 

 Scale of the Astronomical Society, which for 39.37 inches is .00076 

 inch longer than the Imperial Yard. 



(e.) That the value given by Mr. Chisholm involves the errors of 

 transfer to the bar of Baily's metal. 



(/.) That the lines on the bar of Baily's metal do not admit of great 

 precision in comparisons with moderately high powers. 



(g.) That the original iron meter has never been compared with the 

 Meter of the Archives, but only with the Meter of the Conservatory. 



In view of these facts, it does not seem too much to say that it is at 

 present impossible to assign any value to the equation between the yard 

 and the meter, which is not liable to an error as great as .005 inch. 



Finally, the confusion with regard to this relation has become so 

 great, that, by an act of Parliament passed in 1878, the relation found 

 by Kater was declared to be the legal relation, without regard to the 

 various determinations which have since been made. 



I will close this article with an abstract from the Philosophical 

 Transactions for 1798, p. 180, giving the errors of the six-inch spaces 

 of Troughton's scale as determined by Shuckburgh. As this scale is 

 understood to be still in existence, it would be interesting to have a 

 remeasurement of these spaces with a comparator of modern construc- 

 tion. I know of no modern graduations which have a much greater 

 apparent accuracy than is here indicated. 



Inches. Enw,orTCITerenoe 



from the Mean. 



to 6 -f.00012 inch. 



6 to 12 +.00000 



12 to 18 +.00007 



18 to 24 —.00013 



24 to 30 —.00006 



30 to 36 +.00020 



36 to 42 —.00033 



42 to 48 +.00007 



48 to 54 —.00003 



54 to 60 +.00010 



Harvard College Observatory, April 14, 1880. 



