EQUIPMENT. 



Fig. 1.— Brooke's De- 

 tacher, ^igsbee.) 



M. Brooke, then passed midshipman, devised a very ingenious 

 apparatus (Fig. 1), so contrived as to disconnect, on touching- 

 bottom, the heavy sinker — an old cannon-ball 

 with a hole bored through it — required for 

 running out the sounding-line to great depths. 

 This made it possible to use a very heavy sinker 

 compared to the size of the Kne, because the 

 latter, being instantly freed from the weight 

 on reaching the bottom, need only be strong 

 enouo^h to brino; back the lioht iron rod with 

 the collecting cup attached to it which passed 

 through the sinker. While going down, the 

 cannon-ball was suspended by sHngs from mov- 

 able cranks ; on reaching bottom the end of 

 the line became slack, the weight pulled down 

 the arms, and the sHngs slipped off, leaving the 

 shot behind, and the line free to bring back the small sample 

 of the bottom attached to the armature of the rod. This arma- 

 ture has since been greatly modified and the rod changed to 

 a cylinder by Commander Belknap, so that in the deep-sea 

 sounding-machine as used on the " Blake " quite a large sam- 

 ple of the bottom can now be brought up. The apparatus 

 used by Brooke for detaching has also been greatly improved 

 by Lieutenant-Commander Sigsbee ; his detacher is now at- 

 tached to the Belknap cylinder when deep soundings are made. 

 The principle upon which it works is that of a bell -crank 

 suspended excentrically ; so long as the weight of the shot 

 is suspended from the crank, it cannot be detached, but the 

 moment the extremity of the sounding-cylinder touches bottom, 

 the pressure is relieved and the bell-crank is tripped, the shot 

 slips off, and the sounding-cylinder and detacher alone, weigh- 

 ing together about fourteen pounds, are drawn up to the sur- 

 face, with a small quantity of the bottom which has forced its 

 way into the collecting cylinder. 



The examination of the specimens of the bottom collected by 

 the United States Coast Survey was intrusted at first to Pro- 

 fessor Bailey, and in later years to Mr. Pourtales. The results 

 showed at once how large a part in the economy of the life of 



