132 GEOGRAPHICAL SURVEYS AND EXPLORATIONS. 



to send men from headquarters fully equipped, but where officers 

 were summoned from England or distant parts of India this was 

 not possible, and some dissatisfaction was expressed, though the 

 results showed that much excellent work was done by officers who 

 raced up to the front as fast as they could, picking up men and 

 instruments, camp equipage, and horses wherever they could find 

 them on the road, and depending on border natives and even 

 Afghans to fill up the personnel of the party. 



The usefulness of the plane-table for military route surveys during 

 the advance of the troops was fully proved. It is light, portable, 

 and enables the ground to be mapped on the spot. If a good plane- 

 tabler be given a base to start from of which the length and 

 azimuth are known, with a fair proportion of commanding positions 

 end bill peaks susceptible of ready identification, he can survey 

 with great rapidity as he goes along and to a distance much beyond 

 the positions which he may have reached. When, on the other 

 hand, the troops march very rapidly and the route lies through a 

 plain or else a country with hills which are inaccessible, the plane- 

 table is at a disadvantage compared with a theodolite. In all rapid 

 surveys occasional checks in the shape of astronomical observations 

 fur latitude and azimuth and longitude observations as well are 

 desirable. For this occasion several officers in Afghanistan were 

 supplied with a 6-inch transit theodolite, an instrument with a 

 complete vertical circle and an eye-piece fitted with a pair of 

 •• sub-tense micrometers," which are intended to measure small 

 angles subtended by distant objects iu the field of the telescope. It 

 is described in General Thuillier's " Manual of Survey for India " 

 (3rd edition, page 132). also in " Hints to Travellers " by the Eoyal 

 Geographical Society (4th edition, page 33). It may be called a 

 universal instrument, for it is not only well fitted for astronomical 

 lions as well as the ordinary measurement of horizontal 

 angles, but it enables the distances of objects of known length to be 

 detei mined very readily with the aid of the sub-tense micrometers, 

 thus permitting measuring chains to be dispensed with in running 

 traverses and measuring base-lines. It weighs 31 lbs. when packed in 

 its box, the stand weighing 10 lbs. more, and is, probably, the lightest 

 instrument yet constructed capable of such universal application. 



On the conclusion of the Treaty of Gandamuk the surveyors were 

 engaged at Alussoorie, bringing up their calculations and completing 

 their maps, when the sad intelligence arrived in September 1879 of 

 the massacre of Sir Louis Cava°-nari and the members of the British 



