218 SUPPLY OF SCIENTIFIC INSTRUMENTS. 



turn with two grains, which is a quantity less than the one-millionth 

 of the weight in each pan. It is needless to say that such accuracy 

 requires the highest mechanical skill in the construction, and such a 

 balance, which must necessarily be costly, deserves the greatest 

 possible care in use, notwithstanding that it is so constructed that 

 the pans can be loaded before the knife-edge is brought into contact 

 with the plane on which it acts in weighing. 



Besides the above department in London there is a similar depart- 

 ment in Calcutta called the Mathematical Instrument Office, which 

 receives and takes charge when necessary of all the instruments 

 constructed in Europe for the Survey Department, manufactures those 

 which can be made most economically in India, repairs those which 

 are damaged, and keeps up a stock of serviceable instruments for issue 

 to the Survey and other public departments in the Bengal Presidency. 

 It has always been under the superintendence either of the Deputy 

 Surveyor- General or one of the senior officers stationed in Calcutta, 

 but it was not until 1877 that a report on this branch was issued. 

 Since then the work done has been regularly noticed in the Surveyor- 

 General's Report. In April 1878 the number of instruments in 

 store at Calcutta was nearly 37,000, about a third of which belonged 

 to the Public Works Department and a nearly equal number to the 

 Survey, the remaining third being distributed among other depart- 

 ments. The principal description of instruments issued are : — 



To the Si rtment. — Aneroid barometers, binoculars, 



chains, magnetic compasses, drawing instruments, heliotropes, 

 readiug lenses, plane-tables, planimeters, protractors, flat rules, 

 scales of various sorts, optical squares, telescopes, and theodolites. 



To fJir Marine Department. — Barometers, binoculars, Massey's 

 patent logs, carpenters' rules, drawing instruments, sympiesometers, 

 telescopes, and thermometers (but all in very small numbers). 



To the Military Department. — Pocket aneroid barometers, sketching 

 cases, prismatic compasses, drawing instruments, reflecting levels, 

 protractors, scales of various sorts, pocket sextants, and tapes. 



To the Public Works Department. — Drawing boards, chains, 

 compasses, curves, drawing instruments, levels, protractors, car- 

 penters', rules, flat rules, scales of various sorts, levelling staves, 

 tapes, and theodolites. 



To Miscellaneous Departments, viz., Meteorological Department, 

 Telegraph Department, Educational Department, and others. — 



