DETAIL SURVEYS. 889 



the point of the plummet, the plate being kept in position by a 

 couple of small nails. The man at the lead then pulls slightly 

 on the pole so as to get the exact tension, gently raises and 

 depresses the plummet so that its Y)omt just touches the metal 

 plate, when the surveyor marks the exact position with a 

 sharp pencil. 



Although in the description the modus operandi appears 

 rather complex it is not so in reality, and the measurements 

 can be carried out with fair rapidity, 160 chains per diem 

 being frequently done, with an average error not exceeding 

 •25 link per mile. The main stations of the standard survey 

 should be carefully placed in a certain relation to the building 

 line or side of the street traversed, the traverse hne being 

 parallel with and at a fixed distance from one side of it. 

 Some surveyors advocate the exact centre of the street as the 

 best position for these standard or base line traverses, but on 

 account of the vehicular traffic I am of opinion that it would 

 be an inconvenient position, and consider that about two feet 

 outside the kerb on one side, so that the traverse line clears 

 the awning and verandah posts, is about the best place. 

 When the stations are placed a few measurements should be 

 taken from them to three or four angles of permanent build- 

 ings in the immediate vicinity, so that if destroyed they could 

 be replaced. The stations can be defined in various ways, 

 sunken stones with metal plugs inserted, heavy iron bolts 

 driven firmly in, lengths of gas pipe set in cement, &c. but 

 whatever marking is adopted it should be made as permanent 

 as possible. A good plan is to have the station mark protected 

 in the same way as the ordinary gas and water plugs are, and 

 they should be placed in charge of the municipal councils. 

 Stations so fixed and the traverse lines connecting them form 

 not only the basis of the detail survey, but also permanently 

 mark the alignment of the streets, and so define the frontage 

 boundaries of the properties abutting thereon. The field work 

 having been completed the traverses have to be computed 

 and adjusted to the values of the triangulation by the distri- 

 bution of any errors, which, however, should be very small. 

 A skeleton plan is afl;erwards prepared giving the full 

 particulars of the survey. 



For the detail itself the whole area to be surveyed is divided 

 into blocks, bounded preferentially by streets or natural 

 features, each block not exceeding 28 chains by 17 chains, 

 which is the maximum size that can be drawn on the paper 

 used, on a scale of 60 links to an inch. A tracing, showing 



