Royal Institution. 



the same immersed solid body for them, air and water ; and also 

 that by using the same vessel, as, for instance, the same glass bulb, 

 and filling it successively with various gases and fluids, including 

 always air and water in each series, these included bodies may then 

 have their results reduced and be entered upon .the list. The fol- 

 lowing is a table of some substances estimated on the Centigrade 

 scale ; and though there are many points both of theor}' and practice 

 yet to be wrought out, as regards the use of the torsion-balance 

 described, so that the results can only be recorded as approxima- 

 tions, yet even now the average of three or four careful experiments, 

 gives an expression for any particular substance under the same con- 

 ditions of distance, power, &c. near upon and often within a degree 

 of the place assigned to it. The powers are expressed for a distance 

 of 0*6 of an inch from the magnetic axis of the magnet as arranged 

 and described, and, of course, for equal volumes of the bodies men- 

 tioned. The extreme decimal places must not be taken as indicating 

 accuracy, except as regards the record of the experiments : they are 

 the results of calculation. Hydrogen, nitrogen, and perhaps some 

 other of the bodies near zero, may ultimately turn out to be as a 

 vacuum ; it is evident that a very little oxygen would produce a dif- 

 ference, such as that which appears in nitrogen gas. The first solu- 

 tion of copper mentioned was colourless, and the second the same 

 solution oxidized by simple agitation in a bottle with air, the copper, 

 ammonia and water, being in both the same. 



134-23 

 119-83 



Prot-ammo. of copper 

 Per- ammo, of copper 



Oxygen 17*5 



Air 



defiant gas . . 

 Nitrogen . . . 

 Vacuum . . 

 Carbonic acid gas 

 Hydrogen . . . 

 Ammonia gas 

 Cyanogen 



3-4 

 0-6 

 0-3 

 0-0 

 0-0 

 0-1 

 0-5 

 0-9 

 A glass 18-2 



Pure zinc 

 -^ther . . . 

 Alcohol absolute 

 Oil of lemons 



74-6 

 75-3 



78-7 

 80 



Camphor 

 Camphine 

 Linseed oil 

 Olive oil . 

 Wax . . 

 Nitric acid 

 Water 

 Solution of ammonia 

 Bisulphide of carbon 

 Sat. sol. nitre . . 

 Sulphuric acid . . 

 Sulphur .... 

 Chloride of arsenic 

 Fused borate lead . 

 Phosphorus . . . 

 Bismuth .... 



82-59 



82-96 



85-56 



85-6 



86-73 



87-96 



96-6 



98-5 



99-64 



100-08 



104-47 



118 



121-73 



136-6 



1967-6 



Pliicker in his very valuable paper* has dealt with bodies which 

 are amongst the highly paramagnetic substances, and his estimate 

 of power is made for equal weights. 



One great object in the construction of an instrument delicate as 

 that described, was the investigation of certain points in the philo- 

 sophy of magnetism ; and amongst them especially that of the right 

 application of the law of the inverse square of the distance as the 



* Taylor's Scientific Memoirs, vol. v. pp. 713, 730. 



