NARRATIVE OF THE CRUISE. 



59 



fitted two studs, and on its lower were two holes, so that when one sinker was placed upon 

 another the studs on the upper surface of the one fitted into the holes on the under surface 

 of the other, and the holes through their centres, as well as the grooves 

 at their sides, coincided. (See Baillie sounding machine, fig. 14 B.) 



Sounding Machines. — Two kinds of apparatus for detaching the 

 sinkers were supplied ; one the Hydra rod, before leaving England, 

 and the other, the Baillie rod, at the Cape Verde Islands. 



The Hydra rod (so called from its having been made by the 

 blacksmith of H.M.S. " Hydra," as an improvement on Brooke's rod, 

 the American invention) is a cylinder of brass tubing 1^ inches in 

 diameter and 3^ feet in length (see fig. 13), having at its bottom B a 

 butterfly valve, and at its top a sliding iron rod C 2^ feet in length. 

 On the upper part of this iron rod is a small stud D, with a spring 

 that reaches out to the head of the stud when there is no pressure 

 on it. The sinkers were attached to the rod, and on reaching the 

 bottom they were disengaged. To attach the sinkers, an iron disc 

 or washer E with a hole through it (of a slightly larger diameter 

 than the cylinder of the sounding-rod) was placed over one of the 

 holes in a grating ; a piece of wire (No. 9 gauge), two fathoms in 

 length, was fastened at each end to this disc, and the bight of the 

 wire was left standing up ; on the top of the iron disc a sinker was 

 placed so that the hole through its centre corresponded precisely with 

 that in the disc and grating ; other sinkers F were now added until 

 the weight was sufficient for the supposed depth of water, two sinkers, 

 or 1 cwt., being generally allowed for each thousand fathoms. When 

 the requisite number had been placed in position, one on another, the 

 rod was passed through the hole in their centres, and through the iron 

 disc at the bottom, and the bight of the wire attached to the disc was 

 placed over the stud D on the upper part of the rod (the spring being 

 fastened back with a piece of twine to facilitate this operation), and 

 the rod A on being lifted raised with it, by means of the wire on the 

 stud, the sinkers which were kept in their places by the rod passing 

 through their centres, and by the wire fitting into the grooves at 

 their sides. When the full weight of the sinkers was on the stud, the 

 twine which confined the spring was cut so that it was then only kept back by the weight 

 of the sinkers on the wire. On reaching the bottom the weight of the sinkers no longer 

 rested on the wire, so that the spring pushed it off the stud, and the sounding rod was 

 thus relieved from the weights ; the disc, wire, and sinkers being left at the bottom. 



i " 



Fig. 13.— Hydra 



Sounding Machine. 



