USED FOR INDICATING ALTITUDES. 459 



New tables derived from the above values of the Spanish measures are given in 

 this edition instead of those found in the previous ones. 



In the Argentine Confederation, the Spanish vara was made 



1 Spanish vara = 0.866 metre ; hence 



1 Spanish foot = 0.288667 " 



1 Spanish foot 0.9470703 English foot. 



In Brazil the old Portuguese measures are still in force with only very slight 

 changes for adjustment to the metre. 



1 palmo 0.22000 metre. 



1 vara, 5 palmos = 1.1000 metre or 1 metre 3.030303 vara. 

 " 1 foot, Pe, 1^ palmos = 0.33000 metre or 1 metre 0.9090909 foot, Pe. 



The above information on the old Spanish measures is gathered from Behm's 

 Geographisches Jahrbuch, Band I. and II. The three general " Tables for com- 

 paring the most important measures of length, of distances, and of surface," are 

 taken from the same source. 



At the head of each table will be found the value from which it was computed. 



The tables give directly the reduction of any whole number not exceeding four 

 figures, and larger numbers, within the limits needed for altitudes, by means ot a 

 single addition. 



Example. 



Reduce 25,351 English feet into metres. 



In Table XVII., on the line beginning with 25,000 and in the column headed 

 300, take for 25,300 = 7711.30 metres. 



In the second part of the table, on the line beginning 

 with 50, and in column headed 1, take for 51= 15.54 " 



English feet 25,351 = 7726.84 

 When Clarke's spheroid (1866) is used 



German mile = y 1 ^ equatorial degree = 7421.3802 metres, log 3.87048468 



Nautical league = ^o equatorial degree = 5566.0351 metres, log 3.74554594 

 French league = ^ equatorial degree = 4452.8281 metres, log 3.64863593 

 Naut. or geog. mile = -fa equatorial degree = 1855.3450 metres, log 3.26842469 



The tables for the conversion of fathoms into metres, and for the conversion of 

 metres into fathoms, need the following explanation : The exact equivalent of any 

 desired depth in either measure between 100 and 9900 can be obtained directly from 

 the table ; for any depth below 100, the equivalent can be found by looking for the 

 value corresponding to the same number as though it were hundreds, and then remove 

 the decimal point the required number of places to the left. 



Example. 



Reduce 62 fathoms to metres. 



In the first line of the table under 600 we find 60 fathoms = 109.726 metres. 

 In the first line of the table under 200 we find _2 " = 3.657 " 



Therefore 62 =113.383 

 E 13 



