IV PREFACE. 



In an elementary work of this kind there is not room for 

 much that is new. I have drawn freely upon the writings 

 of many of the best authors. The works to which I am 

 principally indebted, and which are here named for con- 

 venience of reference by the student, are those of Besant. 

 La nib, Rankine, Boucharlat, Weisbach, Cotterill, Bland, 

 Jamieson, Fanning, Pratt, Renwick, Stanley, Tate, Descha- 

 nel, Bossut, d'Anbuisson, Poncelet, Eytelvvein, Prony, 

 Starrow, Goodeve, Galbraith, Gregory, Twisden, Bartlett, 

 Wood, Smith, Olmsted, Morin, Humphreys and Abbot, 

 Fuirbairn, Colyer, Barrow, and the Encyclopedia Britan- 

 nica. 



My thanks are again due to my friend and former pupil, 

 Mr. R. W. Prentiss, of the Nautical Almanac Office, and 

 formerly Fellow in Mathematics at the Johns Hopkins 

 University, for reading the MS. and for valuable sugges- 

 tions. 



E. A. B. 

 RUTGEHS COLLEGE, 



NKW BKUNSWICK, N. J., April, 1885. 



