102 MA THEM A TICS. 



Hydrog'raphy (Gr. hu<Ior, water, and graplto, I write). — The 

 art o\^ forming charts exhibiting a representation of the 

 sea-coast, gulfs, bays, soundings, etc. 



Topography (Gr. topOa, a place, and (/nipho, I write). — Tiie 

 accurate description of some particular place or tract 

 of land. Topography goes into minute details which 

 geography does not enter upon. 



MATHEMATICS. 



Mathematics. — The science of quantity, the science which 

 treats of magnitude and number, or of whatever can be 

 measured or numbered. 



Al'gebra (Arab, ul, the, and gehr, resolution). — The science 

 of ((uantity in general, or univensal arithmetic. 



Altim'etry (Lat. aldts, high, and Gr. metreo, I measure). — 

 The art of ascertaining altitudes by taking angles with a 

 proper instrument, and by trigonometrical calculations with- 

 out actual mensuration. 



Arith'metic (Gr. urithmoa, number). — The science of num- 

 bers, or the art of computation. 



Chorom'etry (Gr. choi-a, a district, and vietreo, I measure). — 

 The art of measuring or surveying a country. 



Con'ic Sec'tions. — That part of mathematics which treats of 

 the properties, measurements, etc., of the sections of a 

 cone. 



Geod'esy (Gr. ge, the earth, and daio, I divide). — That part 

 of practical geometry which has for its object the determi- 

 nation of the magnitude and figure either of the whole 

 earth or of any portion of its surftice. 



Geometry (Gr. gc, the earth, and mctrco, I measure). — The 

 science of magnitude in general ; the mensuration of sur- 

 faces, etc. 



Hypsom'etry (Gr. Jutpsos, height, and metreo, I measure). — 

 The art of measuring the relative or the absolute heights 

 of places upon the surface of the earth, either by the 

 barometer or by trigonometrical observation. 



Mensura'tion. — That branch of applied geometry wliich gives 

 rules for finding the length of lines, the areas of surfaces, 

 or the volumes of solids, from certain simple data of lines 

 and angles. 



Rabdology (Gr. 7-hahdos, a rod, and Zoyo.s, a discourse). — The 



