400 



Mr. A. EL Gibson on the Resistance to 



To test this, the series of experiments (16 to 31, Table Y.) 

 were carried out by the author, the essential results being as 

 follows : — 



No. 



i° F. 



r° abs. 



I'm f. s. 



Sp. 



±Px 

 (observed). 



lp o * 



(calculated). 



19 ... 



18 ... 



212 

 32 



673 

 493 



io-i 



10-1. 



1-22 

 111 



1-10 



1-09 



21 ... 



20 ... 



212 

 ~32 



673 

 493 



5-5 

 5-5 



•597 

 •520 



115 



109 



2 



23 ;;] 



22 ... 



66 



212 



' 74 



527 

 673 

 535 



8-43 

 8-43 

 8-43 



•893 



•978 

 •889 



•91 

 1-10 



•94 

 1-08 



25 ... 

 24 ... 



212 

 60 



673 

 521 



7-23 

 7-23 



•828 

 •732 



1-13 



1-07 



In this series of experiments the mean difference between 

 the calculated and experimental results is 3'4 per cent. 



No. 



t°F. 



r° abs. 



v m f. S. 



Sp. 



1-28 

 (observed). 



•72 -28 



26 ... 



27 ... 



32 

 212 



493 

 673 



1095 

 10-14 



1-22 

 1 -22 



M0 



109 



28 ... 



29 ... 



32 

 212 



493 

 673 



7-91 

 723 



•810 

 •810 



1-12 



109. 



30 ... 



31 ... 

 1 ... 



66 



212 



66 



527 

 673 



527 



6-10 

 5-56 

 6-09 



•595 

 •595 

 •591 



112 

 •89 



106 



•94 



In this series the mean difference between calculated and 

 experimental results is 3*6 per cent. 



Since in every case the proportional difference diminishes 

 as $p increases, and hence as the probable proportional error 



* As indicated by the experiments of Dr. Grindley and the author, the 

 viscosity of dry air between 32° F. and 212° F. is given very approxi- 

 mately by the formula 



U=f341 + -518£)10- 9 ft. lb. wt. units, 



this giving- results within 1 per cent. 

 The following are a few values of /* : — 



t° F 



32°. 66° 



212° 



10 9 X)« ... 



355 



375 



447 



