should always be loosened. When the instrument has been leveled, 

 however, it may be set down, not too tightly, against the ring, 

 merely as a precautionary measure. The plate bubbles may still 

 be controlled within one or two divisions. (See I, p. 62, also p. 18). 



The Declinatoire 



For much of the ordinary class of surveying, engineers are be- 

 ginning to feel that while a more serviceable instrument than the 

 compass has never been devised for rapid and approximate orienta- 

 tion, still it has occupied a too conspicuous place, considering its 



79 



capabilities. The primary object of any compass instrument is the 

 determination of the magnetic meridian. Having found it, magnetic 

 bearings can be more accurately read from the graduated circles of 

 the instrument; so that when we consider the merits of the case we 

 can mainly ascribe the persistency of the compass to the inertia of 

 precedent, its admitted value in checking the vernier readings of 

 careless operators, for ruuning rough traverse over cheap property, 

 and preliminay lines in re-location. 



140 



