35 



small angles under which very remote moun- 

 tains appear ; 



A sextant by Ramsden, of ten inches radius, with 

 a silver limb, and telescopes which magnify 

 from twelve to sixteen, times ; 



A snuff box sextant by Troughton, of two inches 

 radius, with a nonius divided into minutes, 

 telescopes which magnify four times, and an 

 artificial horizon of crystal. This small instru- 

 ment is very useful for travellers when forced 

 in a boat to lay down the sinuosities of a ri- 

 ver, or take angles on horseback without dis- 

 mounting ; 



A reflecting and repeating circle by Le Noir, of 

 twelve inches diameter, with a mirror of plati- 

 na* ; 



A theodolite by Hurler, the azimuth circle of 

 which was eight inches in diameter ; 



An artificial horizon by Caroche, of plane glass, 

 six inches in diameter, with an air-bubble le- 

 vel, the divisions of which are equivalent to 

 two sexagesimal records ; 



A quadrant by Bird, with a radius of a foot, fur- 

 nished with a double division of the limb into 

 ninety and ninety-six degrees, the microme- 

 ter screw indicating two sexagesimal seconds ; 



* I have compared in another place the advantages and 

 disadvantages, in long journeys, of the reflecting instruments 

 and astronomical repeating circles. (Aslron. Observ. Introd. 

 t. i, p. 17.) 



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