6 LIGHT SCIENCE FOR LEISURE HOURS. 



of mathematical acquirement necessary for making 

 discoveries and that which is requisite for understand- 

 ing what others have done. That the study of mathe- 

 matics, and their application to astronomy, are full of 

 interest, will be allowed by all who have devoted their 

 time and attention to these pursuits ; and they only 

 can estimate the delight of arriving at truth, whether 

 it be the discovery of a world or of a new property of 

 numbers.' 



It cannot be doubted that Mrs. Somerville here indi- 

 cates her belief in the possibility of presenting her 

 subject in a form suited to the capacities of a large 

 number of readers, and to some extent advocates this 

 as her object. Whether she succeeded or failed in this 

 purpose must therefore be the first question to engage 

 our attention. Sir John Herschel considers that she 

 succeeded, 4 for all those parts of her subject, at least, 

 which the work ' professes to embrace, that is to say, 

 the general exposition of the mechanical principles 

 employed, the planetary and lunar theories, and those 

 of Jupiter's satellites, with the incidental points natu- 

 rally arising out of them.' With the utmost respect for 

 the authority of one who was so thorough a master of 

 the subject which Mary Somerville endeavoured to 

 popularise, I venture to express a different opinion. 

 I find it impossible to come to any other conclusion 

 than that, as respects the main purpose of her work, 

 Mrs. Somerville failed entirely; though I hasten to 

 qualify this statement by the remark that, in my 

 opinion, success was altogether impossible. I believe, 



