382 



Holborn and Day — Expansion of Certain 



The agreement in the observations up to 750° is most satis- 

 factory throughout ; in the interval between 750° and 1000°, 

 however, a discrepancy appears between the observations in the 

 two oven tubes amounting to 1 per cent of the total expansion. 

 The expansion X s of the bar (in /j) may be expressed by the 

 quadratic formula 



X s =4-288« + 0*000640« s (/*) 



The mean distance between the marks on the two ends 

 amounted to 483'5 mm at 0°, hence the expansion* of a unit bar 

 would be 



A=|8868£4-r324£ 2 }10- 9 



Benoitf obtained for the expansion of pure platinum measured 

 between the temperatures 0° and 75° by Fizeau's method, the 

 formula 



X={890U+l-2U a }10-' 



The expansions obtained by extrapolation of this formula do 

 not differ from ours by an amount equal to 1 per cent until 

 1000° is reached — a remarkable agreement considering the 

 magnitude measured and the range of temperature involved. 



2. Palladium. 



The measurements upon palladium are contained in Tables 

 Ila and II& and were all made in the second oven tube except 

 the preliminary heating at the beginning. For this, values of 



Table Ila. 

 Palladium Bar. 



June 26 



June 28 



19*6° 

 1810 MV 

 4083 

 6571 

 9339 



18-8° 

 1923 MV 

 4072 

 6552 

 9345 



M 



(mm.) 



1-349 

 1-432 

 1-197 



1-689 



1-212 

 1-305 

 1-928 

 2-313 



M' 

 (mm.) 



0*036 

 0*176 

 0-526 

 0-197 



0-239 

 0-224 

 0-205 

 0-424 



2 

 (mm.) 



1-385 

 1-608 

 1-723 



1-886 



1-451 

 1-529 

 1-723 

 1-889 



19-6° 



1819MV 



4098 



6585 



9343 



18-8° 

 1927 MV 

 4085 

 6555 

 9348 



M 

 (mm.) 



1-362 

 1-434 

 1-198 

 1-718 



1-199 

 1-347 

 1-934 

 2-322 



M' 

 (mm. 



0-018 

 0-177 

 0-515 

 0-172 



0-252 

 0-198 

 0-222 

 •0-428 



2 

 (mm.) 



1*380 

 1-611 

 1-713 



1-888 



1-451 

 1-545 

 1-712 

 1-894 



* The earlier formula published elsewhere (loc. cit., p. 174) was based upon the 

 observations with the first oven tube only. 



f Benoit, Trav. et Mem. du Bureau international, vi, 1, 1888. 



