Notices respecting New Books. 469 



tion. The extent to which the subject is treated by Montucla is 

 rather what might have been expected in a general history of mathe- 

 matics than what is due to the subject. Still less can we find any- 

 thing consecutively historical, and reaching to our own time, on the 

 matters which constitute what is properly called physical astronomy. 



Astronomy ought to be divided into geometrical, mechanical, and 

 physical. To the first belongs all that concerns the determination 

 of the actual places and motions of the heavenly bodies, without 

 reference to their action on each other ; together with all that relates 

 to the use of such knowledge in the determination of latitude, lon- 

 gitude, and time. To mechanical astronomy (Me'canique Celeste) be- 

 longs the consideration of force or attraction, as an immediate main- 

 taining cause of the order observed ; being, in the widest sense, the 

 theory of gravitation. To physical astronomy belongs all that is not 

 geometrical nor mechanical ; including the consideration of all optical 

 phenomena except change of place, &c. By a curious misnomer, 

 which we believe is due to Woodhouse, the term physical astronomy 

 has been exclusively applied, in this country, to the theory of gravi- 

 tation and its consequences. Mr. Grant has included this theory, 

 together with a great deal of what is more properly called physical, 

 in his valuable work. 



Delambre, as is well known, did not treat the question of the pro- 

 gress of Newton's system. His article on Newton, in the Astr. au 

 18ieme Siecle, shows plainly that he did not feel himself at home. 

 He, usually the independent, stern, and sententious judge, there rests 

 on Clairaut as on a staff; and seems happy when he can escape 

 among the spherical triangles. We do not suppose that Delambre 

 had ever paid much attention to mechanical astronomy, except to 

 receive its results for use. He was above all men who ever wrote 

 in his knowledge of the history of geometrical astronomy, and in 

 his familiarity with the processes of all time. But he left the mecha- 

 nical field quite open. Bailli, who is to a greater extent the histo- 

 rian of this last subject, has not been so much read as he deserved, 

 which arises from the disadvantageous impression created by his 

 ancient fictions and his Indian exaggerations. The third volume of 

 his modern history, and the continuation by Voiron, formed, previously 

 to Mr. Grant's publication, the most extensive separate history of 

 the theory of gravitation. The precis of Laplace, and the historical 

 summaries in the fifth volume of the Mecanique C6leste, are not for 

 the general reader, even if a mathematician. M. Narrien's histo- 

 rical account of the origin and progress of astronomy, an excellent 

 work, hardly goes beyond the time of Newton, except in a very sum- 

 mary manner. The history of astronomy already in the Library of 

 Useful Knowledge, written by Dr. Rothman, was a valuable acces- 

 sion to the means of the English reader ; but it does not touch the 

 main subjects of the present work in any detail. Thus it will appear 

 that Mr. Grant has chosen a field in which he has had no imme- 

 diate predecessor. 



There are many works as to which it is the object of our notices 

 to put before the reader such an account as will enable each one to 



