CHAPTER I 



INSTRUMENTS AND FITTINGS 



Sextants and Stands — Horizon — Theodolite — Station Pointer — Scales — 

 Straight-edges — Chains — Protractors — Pocket Aneroids — Heliostat — 

 Ten-foot Pole — Range-finders — Drawing-Boards — Weights — Transfer 

 Paper — Paper — Books — Chronometers — Marks — Boat's Fittings — 

 Lead-lines — Beacons. 



In preparing for any surveying work, whether in a regularly Errors of 

 fitted surveying ship or not, the first thing is to test all instru- mentsto 

 ments and ascertain their errors. To do the former well, it is be ascer- 

 necessary to have an intimate knowledge of the points on 

 which each instrument is liable to go wrong, which is only 

 thoroughly to be learnt by experience ; but a few hints will 

 assist the beginner. 



A thorough acquaintance with the construction of instru- 

 ments will save many an hour, lost by one whose instrument 

 has gone wrong while in the middle of his work, and spent in 

 fruitless efforts to make out where the fault lies. 



No instrument, not even engine-divided protractors, can beNoinstru- 

 assumed to be Avithout error, and are seldom found so, and perfect, 

 though those errors may be small, in some cases they are of 

 importance, and no work can be deemed satisfactory without 

 the knowledge of how much correction should be apphed, in 

 such instances as it may be necessary to do so. 



We shall therefore commence by some observations on instru- Contents 

 ments, and on all materials and fittings required for conducting chapter. 

 a regular marine survey, embodying in these such hints on 

 using each instrument in general, as are likely to be useful, 

 and also some on choosing them that are not mentioned by 

 Heather in his work on Instruments.* 



* " Mathematical Lastruments." J. F. Heather, M. A. Lock wood and Co., 

 London. 



