PREFACE. XI 



value, especially in a work calculated to serve as a key, by means of 

 which, access may be obtained to all the widely scattered treasures of 

 science; and which will enable those, who are desirous of extending 

 their researches in any particular department, to obtain expeditiously 

 all the information that books can atford them. 



It will not be thought surprising, that the execution of this plan, 

 allowino- for some professional engagements of a different kind, and for 

 a variety of accidental interruptions, should have occupied more than 

 three years, from the resignation of the professorship to the publica- 

 tion of the work. Some part of it is in its nature incapable of perma- 

 nent perfection, since the catalogue must require to be continually ex- 

 tended by the enumeration of new publications; and it might perhaps 

 be desirable that an appendix should be added to it at least every ten 

 years: but the lectures themselves may be expected to remain tolera- 

 bly commensurate to the state of the sciences for a much longer pe- 

 riod; since, in investigations so intimately connected with mathemati- 

 cal principles, the essential improvements will always bear a very 

 small proportion to the number of innovations. I do not, however, 

 mean to assert, that the catalogue is by any means complete, even with 

 regard to older works, but I believe that the references, which it con- 

 tains, are at least sufficient to lead those, who may consult the passages 

 quoted, to the works of every author of eminence that has treated of 

 the respective subjects. Nor do I profess to have excluded all refer- 

 ences that are of little importance; but I trust that the number, which 

 I have admitted, will be found inconsiderable; and it would have been 

 very difficult to have rejected any of them, without some chance of 

 omitting others of greater value. 



Whatever the deficiencies of this work may be, I think it right to 

 observe, that my present pursuits will not allow me to look forwards to 

 any period, at which I shall be able to remove them, or even to attend 

 to the correction of the press, or the revision of the engravings, in case 



