18 



Mr. J. H. Poyntmg on a method of [Nov. 21, 



At the close of the experiment cl was found to be 22'216 centimetres. 

 We have therefore — 



log A=log C. 



+ log 46-61. 



—log 1-26. 



-2 log 22-16. 



= 1-8951337. 



+ 1-6684791. 



-0-1003705. 



-2-6937226. 



= •7695197. 

 .-.A =5-882. 



I have made in all 11 experiments with this method. The resulting 



values of A are — 



May 20 



. . . 5-393. 



i, 23 



5-570. 



„ 24 , . 



4-415. 



„ 28 .... 



, .. 7-172.' 



„ 29 



5-109. 



„ 29 



6-075. 



» 30 



, 5-882. 



., 30 



. 6-336. 



June 5 



,. .. 5-977. 



„ 5 



5-580. 



„ 6 



. ... 5-100. 



The resulting mean value of the mean density of the earth is 5*69. 



If the eleven determinations be supposed to have equal weight, the 

 probable error of their value is 0'15. 



The various determinations differ very much among themselves, but 

 they seem to me sufficiently close to justify the hope that with a large 

 balance and a large weight, which will not be so easily affected by air 

 currents, and with greater precautions to prevent those air currents, a 

 good determination of the mean density of the earth may ultimately 

 be obtained by this method. 



