151 The Nautical Indicator, 



NEW NAUTITAL INSTRUMENT. 



To Mr. Tillock, 



Sir, — In order that the instriiment offered to your notice rnay 

 become as useful to mariners and travellers as the problem on 

 ■^vhichit is grounded was to the inventor and his shipmates in tiie 

 3ear3 1813 and 1814, he respectfully solicits the publication of 

 this in your very useful Magazine. 



The instrument alluded to is called a N.utical indicator, and 

 is a representation of the circles and arclies of the natural hemi- 

 sphere, as far as they are necessary to the seaman and traveller, 

 and when set to observe altitudes of the sun, or of a star, at any 

 time of the dav or night, gives a distinct view of the meridiaa 

 altitude ; zenith diiitance ; azimuth ; amplitude ; true time ; 

 length of the day, and variation of the needle at the place of 

 observation, without the possibility of (unwilful) error ; by placing 

 the whole under the eye of the observer in their natural positions. 



To a traveller by land, no other accoinpanying instrument 

 than a spirit level is necessary, to ascertain all the abovenicn- 

 ttoned articles. At a time when perhaps the luind is too muc!> 

 agitated for numerical calculation, it will in two or three minutes 

 remove every uncertainty with respect to place ti,t one observ;i- 

 tion. 



To the curious in his study, it will readilysolve many important 

 problems in both geography and astronomy as well as naviga- 

 tion, among which the progressi\c variation of tiie magnetic 

 needle is not the least. 



To the teacher in liis school, this instrument will be of much 

 benefit, in detecting the errors of his pupils, and giving them a 

 cleai- demonstration — that, with the observed altitudes, the in- 

 terval of time between each, and the knov.-n declination at that 

 time, the sun is precisely at the same distance from the meri- 

 dian, and that the meridian altitude can be no other than that 

 given by the instrument, as also all the foreni€ntioned objects 

 indispensably necessary to navigators. 



To merchants this mvcntion must be of the utmost coiiso- 

 quencf, since by death, sickness, or casualties, the charge of 

 their ships and cargoes ofren devolves on those whose knowledge, 

 through want of proper education, is far from being adequate to 

 the trust. — ^The instrument is of the most simple construction, 

 ;ind the application n.ay be understood by almost any capacity 

 in a few hours — by a mariner at first sight. 



Any gentleman willing to patronize this invention, will please 

 to address to James Hunter, No. 9, Leicester- street, Leicester- 

 vjuare, London; cr at Mv. John Thin's, ajrchitect and builder, 

 Edinburgh, 



DISEASES 



