SUPPLY OF SCIENTIFIC INSTRUMENTS. 219 



Aneroid barometers, chains, drawing instruments, prismatic com- 

 passes, surveying compasses, protractors, flat rules, scales of various 

 sorts, pocket sextants, tapes, thermometers, and wind-vanes. 



The rates at which instruments were locally purchased in Calcutta 

 in 1879 were, on the average, about 34^- per cent, higher than those 

 at which the instruments received from England had been issued to 

 the public service, and which were themselves 20 per cent, above 

 their English prices, in order to cover freight and other charges. 

 Moreover, the articles purchased in the local market were seldom 

 equal in quality to those received from England. 



The departmental manufactures, valued at about 10,000 Es. in 

 1878, and consisting chiefly of chains, hand map-printing machines, 

 drawing boards, plane-tables, pluviometers, stands for compasses, 

 plane-table telescopes, &c, were issued, as far as could be ascertained, 

 at about two-thirds of the value at which similar articles could be 

 issued if procured from England. In repairing too a very consider- 

 able amount of work is done, i.e., about twice as much as in 

 manufacturing. Among the repairs was that of the great 24-inch 

 theodolite which was used with great success by Colonel Bran fill in 

 Southern India, and among the new instruments manufactured was 

 an idiometer, designed by Lieutenant- Colonel W. M. Campbell, R.E., 

 the object of which was to afford means of measuring the absolute 

 personal equations in observations of star transits recorded on a 

 chronograph. The general arrangement is that of a moveable 

 frame carrying vertical wires in imitation of the wires of a telescope, 

 which passes in front of a fixed imitation star ; a small observing 

 telescope is attached to the wire frame so as to follow its 

 movements, and thus the appearance of fixed wires and a moveable 

 star is obtained. As each wire passes the star two signals are 

 recorded on the chronograph, one by the observer and the other 

 automatically by the instrument. 



In 1884 a fine circular dividing machine by Troughton and Simms, 

 which had been obtained from England some years previously for 

 the Madras Public Works Department workshops, and had lain 

 there unused, was transferred to the Mathematical Instrument 

 Office, where it was set up. It proved to be of great use, enabling 

 the limbs and verniers of many damaged theodolites, which 

 would otherwise have had to be rejected or sent to England for 

 repair, to be re- divided. In the following year a machine was 

 imported from England for the purpose of testing all aneroid 



