afid Traverse Worker. 431 



that it will evidently furnish accurate results within the limits 

 which ordinary observations at sea justify us in anticipating. 

 It may be used either instead of computations, or to excite in 

 the inexperienced a confidence in their calculations, by easily 

 verifying their correctness ; and on both accounts it may, in 

 my humble judgement, be found serviceable to seamen in the 

 navy. East India, or merchant service. 



(Signed) " Olinthus Gregory, LL.D,, 



Prof, of Mathem. &c. 

 "Royal Military Academy, Woolwich, August 16, 1830." 



"London, 11th Oct. 1831. 



*' In compliance with your wish that I should give my 

 opinion on the instrument invented by you for resolving plane 

 right-angled triangles, I beg to state that I think the principles 

 on which the instrument is constructed perfectly correct : and 

 I am of opinion that it will give the quantities, usually taken 

 out of a traverse table, with sufficient accuracy for all the 

 common purposes of navigation. I am likewise of opinion 

 that in many cases the results may be obtained J7wre easily and 

 expeditiously than by a traverse table. 



(Signed) " T. L. Tiarks, F.R.S." 



" Mr. Crow, &c." 



"Frederick Place, Hertford Road, Oct. 14, 1831. 



" I have been much pleased with the instrument you showed 

 me yesterday ; there can be no doubt of the correctness of its 

 principles, and it admits of quite as much accuracy in the con- 

 struction as is requisite ; it is therefore a most valuable auxi- 

 liary to the plain practical sailor : with it he can readily solve 

 any problem reducible to plane trigonometry, and will con- 

 sequently be enabled to work his reckoning every day on deck, 

 and without the aid of books or tables ; a very great conside- 

 ration, particularly in merchant vessels. This may in all cases 

 be done at noon : for he will want nothing in addition to his 

 meridian altitude, except the variation of the compass, which 

 he can get sufficiently near by taking the mean bearing of the 

 sun when at the same altitude, a few minutes before and after 

 its passage of the meridian, when its motion in azimuth is 

 quickest. Wishing you every success in its introduction, &c. 



(Signed) " P. Lecount, Lieut. R.N., F.R.A.S." 



" To Mr. Crow, &c." 



" I have examined Mr. Crow's instrument, and I have no 

 hesitation in stating that by means of it all problems may be 

 resolved wliich are usually resolved by the traverse tables, 

 and that the results from llie instrument will be much more 

 accurate than those that can be obtained from a traverse table, 



in 



