COMPASS 



1521 



COMPOSITE FAMILY 



west, southeast and southwest. The degrees 

 are marked from zero to 360, starting at the 

 north and going round the card in the same 

 way that the hands of a clock move. The 

 combination of card and needles is enclosed in 

 a brass box and it is so pivoted that no matter 



FACE OF MARINER'S COMPASS 



how much the ship may change its position, 

 the compass card always remains horizontal. 

 As an aid to navigation, the degrees are fur- 

 ther divided into points, half points, quarter, 

 points and in some cases even eighth points. 

 If required to steer in a northeasterly direc- 

 tion the steersman by use of the rudder brings 

 the bow of the ship into a direct line with the 

 point marked N. E. on the compass card and 

 the center of the wheel. 



Deviation of the Compass. This term indi- 

 cates error in direction or pointing of the com- 

 pass, caused by the magnetism of the ship on 

 which it is placed. Such deviation does not 

 occur to any appreciable extent in wooden 

 ships, unless the cargo contains a large amount 

 of iron. In vessels built of iron, however, the 

 deviation is sufficient to cause a decided error 

 in direction of steering. Some compasses are 

 so delicately adjusted and so sensitive that 

 metal in the pocket of a steersman has been 

 known to cause an appreciable deviation. 

 Compasses used in iron vessels are carefully 

 corrected, and the deviation is noted on charts 

 so that the navigator can readily calculate the 

 exact direction in which the ship is headed. 

 Sometimes the error or deviation is so slight 

 that mechanical correction of the compass is 

 not necessary. In other cases, however, it is 

 essential that the deviation be counteracted 

 96 



by placing bars of magnetic steel beneath it in 

 such a manner as to cause the compass, when 

 stationary, to point directly towards the mag- 

 netic pole. Deviations are also caused by the 

 natural attraction of the earth. The power of 

 such attraction varies in different latitudes. For 

 the benefit of navigators, charts are provided 

 which indicate the natural deviation to be 

 expected in all latitudes. 



Boxing the Compass, a term applied to abil- 

 ity to repeat the names of all the points, half 

 points, quarter points and eighth points of the 

 compass, in their proper order. This is an 

 accomplishment required of sailors, especially 

 those called upon to steer vessels. The origin 

 of the term is not known, but it is probably 

 due to the fact that the compass on board 

 ship is contained in a brass box. 



Surveyor's Compass. This form of compass, 

 used only on land, consists of a magnetic 

 needle moving over a disk on which, in addi- 

 tion to cardinal and intercardinal points, de- 

 grees, minutes and seconds are marked. The 

 method of use is exactly similar to that on 

 board ship, except that the surveyor's compass 

 is fitted with a system of levels and screws 

 by which its position is ascertained and regu- 

 lated so that it may remain perfectly horizon- 

 tal while in use. F.ST.A. 



COMPOS 'ITE FAMILY, or COMPOSITAE, 

 kompoz'itee, the largest family of flowering 



SOME MEMBERS OF THE COMPOSITE 

 FAMILY 



(a) Goldenrod (d) Sunflower 



(b) Cosmos (e) Dandelion 



(c) Dahlia 



plants, containing over 12,000 known species 

 one-tenth of the species of flowering plants in 

 the world. They consist of herbs or shrubs 



