Mr. Lubbock on the Theory of Double Refraction. SS 1 



complexity, and therefore easily manag«»able, and not liable 

 to derangement. They also take up very little room. As 

 yet the extent of power of which they are capable has not 

 been at all ascertained, as the size of battery employed is so 

 trifling and the magnets so few : but from what can be 

 judged by what is already done, it seems to be probable that 

 a very great power, in no degree even inferior to that of 

 steam, but much more manageable, much less expensive, and 

 occupying greatly less space, if the coals be taken into ac- 

 count, may be obtained. 



" In short, the inventions of Mr. Davidson seem to be so 

 interesting to rail-road proprietors in particular, that it would 

 be much for their interest to take up the subject, and be at 

 the expense of making the experiments necessary to bring 

 this power into operation on the great scale, which indeed 

 would be very trifling to a company, while it is very serious 

 for an individual by no means rich, and who has already ex- 

 pended so much of his time and money from the mere desire 

 of perfecting machines which he expected would be so bene- 

 ficial to his country and to mankind. For it deserves to be 

 mentioned that he has made no secret of his operations, but 

 has shown and explained all that he has done to every one 

 who wished it. His motives have been quite disinterested, 

 and I shall deem it a reproach to our country and country- 

 men if he is allowed to languish in obscurity, and not have an 

 opportunity afforded him of perfecting his inventions and 

 bringing them into operation, when they promise to be pro- 

 ductive of such incalculable advantages*. 



" I am, my dear Sir, yours, &c. 

 Michael Faraday^ D.C.L., S^c. S^c." " Pat. Forbes." 



(( 



LIII. On the Wave-surface in the Theoty of Double Refrac- 

 tion. By J. W. Lubbock, Bsq.^ F.R.S.f 

 T N the L. and E. Phil. Mag. for November 1837, (vol. xi., 

 ■* p. 417) I endeavoured to present in a concise form the 



♦ [We would observe on the subject of the above communication, that 

 as the late Dr. Schulthess (1833), Prof. Botto (1834), and Dr. Jacobi (1835), 

 whose papers on the application of electricity as a mechanical power have 

 been given in Taylor's Scientific Memoirs, vol. i. p. 503, &c. and vol. ii. p. 1, 

 have given full details of the means they employed, the results obtained, and 

 the cost of the apparatus, it is to be desired that we should be furnished 

 with similar information regarding Mr. Davidson's invention, in order that 

 impartial persons may be enabled to form a judgment on the relative merits 

 of each. A paper by the Rev. J. W. M'Ganley, on the application of mag- 

 netism as a moving power, read before the British Association in 1835, will 

 be found in L. & E. Phil. Mag. vol. vii. p. 306, and another, communicated 

 in the following year, in the " Sixth Report" of the Association Transactions 

 of the Sections, p. 24. Edit.] 



t Comnmnicated by the Author, 



