14(3 SATURDAY LECTURES. 



lead. When sounding is done with hempen-line, and a 

 sounding Aveight of fift}^ or one hundred pounds, it will be 

 apparent that the friction of two or three miles of line, with 

 its tags and instruments attached, inust be enormous, even 

 if it could be hauled up perpendicularly in still water. But 

 when the vessel, as she alwa^'s must, drifts a little, and the 

 line comes up in a diagonal direction, the friction, added to 

 the weight, renders the safe recovery of the line, sounding- 

 cup, and thermometers or w^ater bottles attached to it — a 

 matter of great difficulty, some uncertainty, and several 

 hours of time. In anything but the best of weather such 

 work becomes almost impracticable. 



Mr. Brooke's invention included an ingenious and simple 

 apparatus for detaching the weigjit at the bottom of the sea, 

 and leaving it there. Having thus to haul up only the line 

 and the light tube containing the sample of the bottom, 

 the labor was greatly diminished, and the time of hauling 

 in much shortened. Brooke's apparatus has formed the 

 basis of the only really successful sounding-cups which are 

 now in use either by our own or foreign navigators. Im- 

 provements on the original form were successively made by 

 Capt. Shortlancl, of the British navy, Capt. Belknap, of 

 our own nav}^, and lastly by Lieut. Com. Sigsbee, U. S. N., 

 while engaged in the service of the Coast Survey. The in- 

 strument, as perfected by Belknap and Sigsbee, does not 

 seem capable of much further improvement, and works to a 

 charm. The accessory machinery for use in deep-sea sound- 

 ings, such as small engines, reels for the line, blocks, and 

 elastic arrangements of rubber or steel springs to guard 

 against the effect of sudden jerks upon the line, have been 

 improved from time to time, and are fully described in pub- 

 lications on the subject by Sir Wyville Thomson and Lieut. 

 Com. Sigsbee. The most important improvement of recent 

 date is due to the distinguished Professor Sir William Thom- 

 son, of Glasgow, in 1872. This consists partly in the em- 

 plo^anent of fine steel piano-wire for the line inst,ead of rope, 

 and partly in the method of its use. Instead of the tags on 

 the line to determine the length run out, the latter is known 



