334 Mr. P. E. Chase on Gravity and l Magnetic Inclination , 



It would certainly be very satisfactory, if it were possible, to 

 have some means of exhibiting, by simple laboratory experi- 

 ments, the direct and mutual convertibility of gravitation and 

 magnetism ; but I fear the attempt to reproduce, in any appre- 

 ciable mechanical form, the magnificent and daily repeated ope- 

 rations in the laboratory of nature which I have feebly endeavoured- 

 to interpret must always be futile. In order to obtain even the 

 small amount of disturbance (-00134) which I have noted in the 

 half-daily variation of atmospheric weight (Trans. Amer. Phil. 

 Soc, vol. xiii. p. 121), it would be necessary to take observations 

 at two stations, one of which should be 2*655* miles more dis- 

 tant from the earth's centre than the other. If the differences 

 of vapour, temperature, barometric pressure, force and direction 

 of wind, atmospheric electricity, &c. did not so complicate the 

 problem as to discourage even the most sanguine experimenter 

 from any attempt at solution, any result that could be obtained 

 under such circumstances would give little general satisfaction. 



It is possible, however, that the end, which we should vainly 

 strive to reach directly, may be indirectly attained. Indeed the 

 various stages of an indirect road have long been known, but we 

 have not been able to compare them by any common measure. 

 The motion of gravity, by percussion or the obstruction of sim- 

 ple fall, has been repeatedly converted into the motion of heat ; 

 and the motion of heat by the thermo-electric pile has been con- 

 verted into the motion of magnetism. The experiments of 

 Barlow, Coulomb, Kupffer, and Christie f on the influence of 

 heat upon the magnet, furnish data that may lend some aid to 

 any investigator who seeks to ascertain the precise value and 

 modification of each force, in these successive conversions. 



But I look most hopefully to researches that are based upon 



* Rx(VD'~\ / D)=3963x(Vl-00134-l)=2-655. At Singapore the 

 daily disturbance of total force is only fi as great as it should be theoreti- 

 cally. I suspect that the discrepancy is owing mainly to the monsoons and 

 other great temperature-disturbances of the station, which shift the lines 

 of force by a kind of conduction polarity. (Faraday, 'Experimental Re- 

 searches,' 3279.) In other important respects there is a satisfactory corre- 

 spondence between Singapore and St. Helena. E. g. : — 





Mean 

 fall. 



Mean tide (Theoretical Xf£). 



Oh. 



6h. 



12 h. 





h m 

 8 29 

 8 23 



-•00031 

 -•00031 



-•000173 

 -•000180 



+•00064 

 +•00064 







(See 'Numerical Relations of Gravity and Magnetism,' Sections V., 

 IX./and Faraday's Experimental Researches, III. 321-2.) 



f See Encyclopaedia Britannica, eighth edition, vol. xiv. pp. 35-39. 



