112 



THE VOYAGE OF H.M.S. CHALLENGER. 



V 



/" 



valve, air being at the same time admitted at the top by the removal of a plug H, from a 

 hole in the upper valve. The lower valve and stop-cock are protected from damage when 

 striking against the ground by the casting extending about six inches below the valve. 

 The arrangement and dimensions of the parts are sufficiently apparent from the wood- 

 cut to make further description unnecessary. The slipping arrangement is in principle 

 the same as that used on Brooke's sounding rod. 



In order to adapt this water-bottle to collecting water at intermediate depths, it is 

 fitted with a slipping plate (see fig. 40), furnished with a metal flap Q, 

 which depresses it when the motion of the instrument is reversed. It 

 is inserted into a slot S, immediately below the usual slipping plate to 

 which the sounding line is attached, and differs from the latter in 

 having a deeper notch R, and having a slot instead of a hole for the 

 reception of the pin T, round which it turns. The object of this slot 

 is, that after the string has been cast free, the flap may fall down close 

 alongside the rod and afford as little resistance as possible in pulling 

 up. In using the instrument, it must be let go before the flap enters 

 the water, and not checked until the depth desired has been reached. 

 On board the Challenger the slip water-bottle was only used to obtain 

 specimens from the bottom. 



The Stop-cock Water- Bottle. — Water from intermediate depths is 

 obtained in an instrument represented in fig. 41. It is made entirely 

 of brass, which, however, might advantageously be nickel-plated. 

 It consists of a cylinder A, terminated at both ends by similar stop- 

 cocks B, B, which are connected by the rod C. This rod carries, near 

 its upper extremity, a piece of stout sheet brass E, 10 centimetres 

 long by 1 5 broad, soldered to the casting F, which is movable about an 

 axis. The function of this part of the apparatus will be more easily 

 explained by describing the manipulations necessary when collecting 

 water. 



When intermediate water is to be obtained, the water-bottle is 

 firmly attached to the sounding line, which carries at its end usually a 

 56 lb. or a 1 cwt. lead ; the stop-cocks are then opened, giving them, with the rod C, the 

 position represented in the left hand figure. The line is then lowered carefully by hand, 

 until the water-bottle is close to the surface, when it is let go, and the line allowed to run 

 out without a check. During its passage downwards, the water courses freely through it, 

 being considerably assisted by the conical end pieces M, M. When the requisite depth 

 has been reached, the line is checked, hauled in a few fathoms, then let go, checked again 

 at the same mark, and finally hauled in altogether by the donkey-engine. When the 



Fig. 40. — Instrument for 

 slipping the Cylinder at 

 intermediate depths. 



