General Instructions for Surveying', possibly written byMajor James Rennell, ca February 1791 (Series 60.05) - No. 0020

[Page 20]

Application of this Quadrant (& in a Boat particularly) is by Mr. Dalrymples Problem; by which when 3 Objects are determined in Relative position to each other 2 Angles between them taken with a Hadley furnish a Station from whence any other Angles may be taken & laid off. In the Case of Soundings it is admirable. And to obviate any objection to practising it When the Surveyor has not 3 Points determined, he has only to reflect that altho' they might not be determined when he took his Angles they may be so afterwards in ye Course of his Operations: for such Objects as are proper for Angles with a Hadley are likely to attract equal Notice as Surveying Marks with a Compass
We come next to the Subject of transient Bearings, or the Act of setting two or more Objects in one line of direction, as they pass over close with or open out from each other; such as Points, Rocks, Shoals, Peaks of Mountains or Islands Cliffs &c of all the modes of taking Bearings there is not a more useful one than this; for in effect it multiplies the number of Stations without the delay of establishing them or of going from one to the other, were it in all cases possible: for Instance, the X positions are or may be determined; & that Islet by passing over a variety of other Objects, & being set in one with each of them, gives a Bearing from the Island to each, the Island being in
this Case  a Station the same as a Station
The 
[note in margin]
X position of an Islet or Rock is ascertained by being set in one with two objects on ye shore whose