W. P. Trowbridge on a new Sounding Apparatus. 7 
flax, or silk of five hundredths of an inch in diameter, may be made to 
bear a strain of 40 or 50 Ibs.; which is abundantly strong for the pur- 
, as the weight and case are left at the bottom, the register and speci- 
men tube only being brought up. 
may be made of tin in sections of eighteen inches 
length, with stove-pipe joints and bayonet fastenings. The object of this 
is to adapt the length of the tube readily to the amount of line which it 
,is to contain. A tube four inches in diameter will contain nearly a mile 
of line to each foot of the tube. 
Sinker and Specimen-tube——The sinker is made of cast iron or lead of 
any desired weight, depending upon the desired velocity of descent. A 
weight of 25 lbs. has been adopted. The sinker is conical and is inserted 
tube by screws or by a bayonet joint and fastening. The weight has a 
conical hole or cavity through its entire length, through which the small 
specimen-tube passes in the manner shown in the drawing. e i- 
men-tube is a tube of thin brass passing through the weight and attached 
to the lower end of the line within the large tube. This specimen-tube 
is fitted with a valve opening upwards in the bottom, which closes when 
the tube is drawn up, thus retaining the mud which is forced into the 
tube when the weight strikes bottom. The specimen-tube fits loosely in 
the hollow of the weight, so that it may be easily drawn out as the line 
is hauled in. 
made to turn in opposite directions and will operate as checks upon each 
