MAGNETISM. 101 



The pp.iratus of many steamers in the wheel house, 



1 ul iron and steel, and these act as the poles of 

 the ship's magnetism. They not only at all times aH'rct the 

 compass, hut the effect varies, as the helm is shifted hard a-port 

 or starboard ; the joints of the screw steering gear sometimes 

 advancing towards, or receding from, the compass, thus attract- 

 ing the north point of the needle, or repelling the south. 

 Again, when steam is up in the boilers, the magnetic influence 

 of the whole machinery is increased by the action from them. 

 Care in observations should also be taken in approaching a 

 rocky iron-bound co.ist, particularly such as that of Nova Scotia, 

 where the S. S. A : l/.ii'f : <- and the City of Washington were lost, 

 because the strata of rock is nearly venical, which in conse- 

 quence allows the escape of mineral emanations from the interior 

 of the earth, to influence the ship's nvign.-tism, and thus to alter 

 her compasses. A considerable deviation might thereby be 

 induced without any apparent cause for it. 



The best safeguard, with due care, would in most instances, 

 be the fixing of a compass at such a distance above the deck, as 

 would be beyond any local influence. And yet with this 

 .:kn, the most absurd mistakes are made, for in many 

 steamers we have seen the compass elevated on the mast, but 

 fixed ihnv under ir-^/t erots trees. They are thus led into the 

 very d , lurli. in elevaiing tho compass, they expected to 



Avoid 



]; sat'iv of lite and property, all sailors in particular, 

 should kno\v iliose simple facts; and all iron vessels should be 

 examined and reported upon, concerning such parts of their 

 construction or fittings, as are liable to derange the compasses. 



