1870.] Notices of Scientific Works. 235 



we recall the intense application of mind and body necessary for the 

 pursuit of physical investigation, and how for forty years Faraday 

 sustained this unceasing drain of nervous energy, our surprise is 

 only at his powers of endurance, and that it should have been 

 possible for one man to accomplish so much. Up to the very end 

 he worked, even when his memory was fading away and his powers 

 of mind so exhausted that he had at frequent intervals to rest his 

 brain, until, like a voltaic pile, the nervous force accumulated, with 

 sufficient intensity to effect a discharge of thought. At last baffled 

 at every turn by the loss of memory, his experimental work only 

 ceased when, after completing a tedious and unsuccessful investi- 

 gation, he found he had done it all before, and obtained the results 

 he now sought for in vain. 



His last thoughts were turned to the possibility of correlating 

 gravity with the other forces. And, with all deference, we beg to 

 express our regret that the Koyal Society refused his last paper, in 

 1860, "On the possible Kelation of Gravity with Electricity and 

 Heat." The results, it is true, were negative, but to publish what 

 cannot be done is, in science, often as valuable as to publish the 

 records of success. Here are some of the speculations that are to 

 be found in Faraday's note-book at this period. Speaking of gravity, 

 he says : — " Might not two globes (or masses, as pigs of lead), 

 A, B, attached to the end of a long rope, passing over a large 

 pulley at the top of the clock-tower, or in the whispering-gallery of 

 St. Paul's, serve an experimental purpose ? Starting with both balls 

 insulated, discharged, and balanced, then it would be easy to raise 

 B and lower A, and examination by a very delicate static electro- 

 meter might show A charged positive and B negative; then dis- 

 charging both, and reversing the motion, B would come down 

 positive, and A become negative, and so on These electro- 

 meters being very delicate and of the condensing kind, one man, 

 having only to turn a windlass, might work the apparatus for half 

 a day, or it might be kept in motion by a steam-engine, or other 

 mechanical power. The evolution of one electricity would be a new 

 and very remarkable thing. The idea throws a doubt on the 

 whole ; but still try, for who knows what is possible in dealing with 

 gravity?" He makes the trial with all his accustomed experi- 

 mental skill, and though he fails he does not despair that others 

 will obtain results that are denied to him. 



In connection with this subject of the correlation of forces an 

 important extract, from the notes of a lecture delivered by Faraday 

 in 1834, is given on p. 48, vol. ii. The notes run thus : — " Now 

 consider a httle more generally the relation of all these powers. We 

 cannot say that any one is the cause of the others, but only that all 

 are connected and due to one common cause. As to the connection, 

 observe the production of any one from another, or the conversion of 



