Magnetic Experiments 29 



of the Royal Society; to Prof. Dewar, Mr P. T. Main, Mr G. F. Rodwell, 

 and Dr E. J. Mills, who gave me information on chemical subjects; and 

 Mr Dew Smith and Mr F. M. Balfour, of Trinity College, and Prof. Ernst 

 von Fleischl, of Vienna, who gave me information about electrical fishes, 

 and the physiological effect of electricity. 



P.S. I4th June, 1879. 



Just before sending this sheet to press I have received from Mr Robert 

 H. Scott, F.R.S., a small packet marked "Cavendish Papers," which had 

 been sent to the Meteorological Office by Sir Edward Sabine. 



These papers relate entirely to magnetism, and do not fall within the 

 scope of this volume*, though they may supply important materials for 

 the magnetic history of the earth, and are in all respects excellent speci- 

 mens of Cavendish's scientific procedure. 



I shall therefore only mention a few particulars in which these papers 

 throw some additional light on Cavendish's life and work. 



The descriptions of Cavendish by Cuvier, Young, Thomson and Wilson 

 agree in representing him as living in London, and regularly attending 

 the meetings of the Royal Society, but in other respects leading an isolated 

 life, very much detached from the interests, whether social or scientific, 

 of other men. 



It has also been hinted that Lord Charles Cavendish, who, as we have 

 already seen, was himself addicted to scientific pursuits, did not entirely 

 approve of his son's devotion to science, or at least, for some reason or 

 other, restricted him in the means of carrying on his work. 



In these manuscripts, however, we have the details of a laborious series 

 of observations undertaken to determine the errors of the variation compass 

 and the dipping needle belonging to the Royal Society, and on Sept. 16, 

 1773, we find "Observations of needle in Garden by Father and Self," 

 and a "Comparison of Society's compass in house and in society's] garden 

 with Father's compass in room." 



It appears, therefore, that Lord Charles Cavendish not only placed his 

 instruments at his son's disposal, but made observations of the compass 

 in concert with him, and that these observations were undertaken in order 

 to make the instruments belonging to the Royal Society more available 

 for accurate measurements. In the same Journal there are also "Measures 

 taken for setting Dr Knight's magnets so that their poles shall be equi- 

 distant from variation] comp[ass] and dipp[ing] need[le] in 1775." The 

 results of this enquiry are briefly stated by Cavendish in his paper on the 

 Instruments belonging to the Royal Society in the "Philosophical Trans- 

 actions" for 1776. In the same volume there is an account of Dr Knight's 

 great Magazines of magnets by Dr Fothergill. 



* [See Dr Chree's account of Cavendish's Magnetic Researches in vol. n.] 



