Appendix.] 



HYDROGRAPHY, 



•J' I 



APPENDIX No. 2. 



Tojind the Height of an Object the Distance ofivhich is known. 



Rule. — To the observed altitude apply the tnie dipj less the terrestrial 

 refraetiou."* The result call corrected altitude ; to the log. of the diJ?- 

 tance in yard?^ add the constant 8*073007, and find the log. of the sum^ 

 which tarn into arc and add to the corrected altitude ; then to the log. 

 tangent of this sum add the log, of the distance in yards as above-nien- 

 tioned, the result will be the log. of the height of the object in yards. 



Example. — Mount Etna was seen at 57 miles distance, and subtended 

 an angle of 1*^ 30' 00" with the horizon ; elevation of the eye 20 f(^eU 

 required the height of the mountain ? 



Distance 57', i)i yKtds 115650 log 5 '063 157 



Constant . . , S "073^^07 



^ ■ 



Altitude ... f 30 

 jDip ..." 4 



00 

 43 



17 

 26 

 43 

 48 



^ 



F- 



t! 



\xx of Dip , , H- 

 Corrected Altitude 1 95 



+ 22 



w 



• • • 



- ^ 



True Altitude . . 1 48 



31 



Tangent , 

 Constant 



60)1368" log=:3'l36154 



Correction , 22,48 



, 8-4993668 



, 5-0631570 



Yards. 



3*5625238 Ic^ 3652 heiijht required. 



X3 



V- 



% 



i- 



10956 feet. 



mm 



*■ r 



APPENDIX No. 3 



2> 



r 



To find the Constant for a Height, in order to compute its Dv^ance 



readily frojn its observed Altitude, 



Kui.E. — Froai the log. of the height in yards subtract the constant 

 log. 6 • 5424481 , halve the sum — find its sine, and take out the correspond- 

 ing co-sine, which is the constant required, (a) 



^-' 



• The terrestrial refraction variVs from | to xi P^^t of the arc. 



f If the Dip Sector had been used, the observed Dip should be substituted for these 

 two quantities. 



