THE PLUMMET. 3 



sounded. In the approaches to some coasts or 

 harbours where dangerous rocks a}>ound, the plum- 

 met is indispensa'ile as a means of discovering the 

 depth and character of the bottom. Is it mud, or 

 sand, or gravel, or rock ? Will it be advisable to 

 cast anchor, or to find a more favourable situation? 

 The plummet will answer these questions. 



In its simplest form this little instrument con- 

 sists of a cylinder of lead, suspended by a cord 

 attached to one of its extremities, while the other is 

 tallowed in order that some portion of the soil at 

 the bottom of the sea may adhere to it. It is 

 simply dropped into the water, and allowed to fall 

 suddenly to the bottom. The imperfection and un- 

 certainty of such an instrument are obvious. If the 

 sea be calm and of slight depth, it may prove equal 

 to its work, and report correctly. But how often is 

 the lead pulled up without anything adhering to it I 

 The sea, in fact, is seldom or never at rest, and at all 

 times there are currents below the surface, which 

 may carry away in a bight hundreds of yards of the 

 line, without indicating that the lead has reached the 

 bottom. 



Various attemj)ts have been made to improve the 

 plummet. The object has been to make quite sure 

 that it shall bring up to the surface a sample of the 

 soil at the bottom of the sea, and to diminish tlie 



