DEPRESSION, 
Y = 89° 57’ 50” ; Having found the depreffion for one foct = go" , a- 
3 = 90 15 30 table may be conftru@ed by multiplying 59”.1 by 
¥—3= — 17 40 ~ height of the obferver. 
4 i a 34 ; Example. 
d—do+ =—- 2.1 = p. 5 Lo " re 
es oe ge. 5O.1 1.77150 
Log. fin. § ¥ — 3 = — 7.40985 $ Log. 245 =1.194.58 
og. K = + 4.97091 
Cof. 3p eased 2. “2.96616 = 925" = 1g' 25. The 
635 2. 2.38075 fame as above. 
“Therefore, B is 240.3 feet below the level of A. 
Example IL. by formula (5.). Table of the Depreffion of the Horizon of the Sea. 
Log. + = 4.97091 
’ ; v, 2. ae y, 
Tang. = 7.40985 S gig ele (Fels Fe a. 
ee Ble Some s tome § ice “§ 
ae = 240.3 feet as above. we e}OEllo ce! O-8 fac] oS loc oa 
wie (be lem|s2| Sn feog) Se ae) or 
When a i is ae Equation (2.) o4 oil | — . 
Let 2 = 0.0 
Ho Ke. (3 + 0.67 C—o.5C), lp ron oon cow 
=K cot. (3 + .433 C) 1.0 59) 38. | 6 4} r43itr 46] 250) 15 34 
eer Bll 24) qu | 6 18) r46irr 54) 255) 15 44 
493 Ca 6 40 af 4 - oe ae : ee 15 53 
ae 4 4 4 152/12 205] I 
5° & |2 12!) 50 | 6 58 r5sjr2 xsi] 2%0] 16 11 
Log. tang. 8’ 50” = 7.40985 = iia 
497091 6 |2 25! 53 | 7 1oll 158i12 22/| 275] 16 20 
2. es = nade 3 feet. 7 {2 36] 56 | 7 22] r61|\12 29]) 280, 16 29 
Example IV 8 |2 47|| 59 | 7 34|| 164]12 36]| 285] 16 37 
? 9 |2 57|| 62 | 7 45]] 167|12 4311 290) 16 46 
ee pie - obferving the depref- 10 13 7| 65 | 7 56] 170112 scl 295] 16 ss 
Let the obferved depreffion be r 257 required the height 1r 13 161, 68 | 8 . . 
‘ef the obferver a the leve of she 12 ; asi 71 | 8 18 ae a _ ae i: Pe 
I+ 2p ' tang.” (F~ 90°). 13 (3 3311 74.) 8 28] 179/13 roll 350) 18 25 
roe ¢ = 9.698 14 13 43) 77 | 8 38] 182/13 371) 375] 1 
roe fo - a 7.08582. T5 13 49]| 80 | 8 48] 185/13 23]] goo) 19 42 
Log. eee 25" = 5.30344 | 16 13 56] 83 | 8 58l 188]13 3cll 425] co 18 
2.38926 = 245 feet. alae 86 | 9 8] 191/13 36) 450] 20 53 
"The three firft termsbeing conftant, v ee oa a 89 | 9 TOTS 43), 475 2E . 
To the conftant log. 7.08582 add twice the log. of the 19 |4 17) 92 | 9 oe re ata 
tangent of the depreffion, and the fum will be the anise 20 [4 241) 95 | 9 39) 200113 55 
of the number of feet required. - rl 08 
the height of the obferver be given, and the depref- s + 37 9°19 aoe a= 79° 23 6 
fion is required, then the rule will be to the log. of the 22 le S71 )PO2 | 9.54) 200 TE 8) ORG) 24 7-5 
height in i add the conftant log. 2.91418, and add like- 23 16 43104 10° 2) 90014. 14) O59 25 5 
wil o the index, then half this fum will be the log. oe aoe fe ee ee ces 
tangent of the depyeffion required. 25 | Faytte (FO 10), 215/14 2G) 75) 20°58 
Example, ~~ 26 |5 11113 [10 28}} 218|14 32/1 800] 27 51 
Let the pueaht of the obferver be 100 feet, required the | 27 |5 7/126 |10 36)) 221)14 38] 850] 23 43 
depreffion 28 [5 3ilt19 |10 44] 224'14 44! goo] 29 35 
Log. x : eanees 29 |5 18lir22 |ro 521) 227/14 Soll gsc] 30 19 
Conf. ion: - 2.91418 390 15 24125 [IT Co} 230/14 §6);1000] 31 9 
14-91418 31 15 29128 [rt 8) 233115 atitgoo| 38 8.5 
Log. tang. of the Depreffion = 9’ 5" — 745799 38 |5 34)131 [tr 16]! 236 i 7||2000] 44 2.5. 
Let the height of the obferver be 245 feet. 33 [5 39}134 JIT 24|) 230/15 13/3000] 53 56 
Og. 245 2.38916 34 45 441137 [LT 3a] 241115 Igilfooo] 1 2 75° 
Conk. log. 2.91418 35 [5 49F49 [TT 3c}} 245/15 25) 5000) 1° 9.38 
5.30334 
Log. tang. 7.65167 ==15' 2 " == depreffion | The formule on a fpheroid would be a little _ from 
required, the fame as in Mr. Mendoza’s table. - the above, but the corre€tions are too {mall to any 
Vor XI 3M Phi 
cal 
