202 Mary Somerville. 



do so while in Paris, I now began the work, and, in 

 consequence, I was led into a correspondence with 

 Mr. Ivory, who had written on the subject, and also 

 with Mr. Francis Baily, on the density and com- 

 pression of the earth. My work was extensive, for 

 it comprised the analytical attraction of spheroids, 

 the form and rotation of the earth, the tides of the 

 ocean and atmosphere, and small undulations. 



When this was finished, I had nothing to do, 

 and as I preferred analysis to all other subjects, 

 I wrote a work of 246 pages on curves and sur- 

 faces of the second and higher orders. While 

 writing this, con amore, a new edition of the 

 "Physical Sciences" was much needed, so I put 

 on high pressure and worked at both. Had these 

 two manuscripts been published at that time, they 

 might have been of use ; I do not remember why 

 they were laid aside, and forgotten till I found 

 them years afterwards among my papers. Long 

 after the time I am writing about, while at Naples, 

 I amused myself by repairing the time-worn parts 

 of these manuscripts, and was surprised to find that 

 in my eighty-ninth year I still retained facility in 

 the "Calculus." 



The second edition of the " Physical Sciences " 

 was dedicated to my dear friend, Sir John Herschel. 

 It went through nine editions, and has been trans- 



