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Proceedings of the Royal Society 
through, it easily, keeping the valves open ; when it is pulled up the 
pressure of the water closes the valves, and if the upward motion is 
uninterrupted keeps them shut. A specimen of water is thus secured 
from nearly the greatest depth to which the apparatus has been sent. 
This form has been worked out in many modifications; arrange- 
ments have been added for locking the bottle when it is full, and also 
for closing it by other means than changing the direction of motion. 
In Marcet’s machine for obtaining bottom samples,* the upper 
and lower valves were connected together, and during the descent 
of the instrument they were kept open by a cord and weight, which, 
ceasing to act on touching the bottom, allowed a spring to close and 
lock the valves. There was thus no risk of the contents changing 
during the upward journey. In a modification for obtaining inter- 
mediate samples the valves (in this case cones fitted on a rigid 
rod) were held up by a catch which could be withdrawn by a lever 
actuated by a weight slipped down the sounding line. The valves 
then closed, and were locked by a catch. 
Wille’sf water-bottle and Sigsbee’s J water-cup are the most ap- 
proved modern developments of Hooke’s apparatus. Wille’s ap- 
paratus raised 5 litres of water, Sigsbee’s only 8 ounces. Both are 
locked by the action of the current in the ascent on small screw pro- 
pellers, which form part of the instrument. Tennant before 1819 
devised a water-bottle § which was closed by the action of the 
water on “ a small fly-wheel during its ascent.” The arrangement 
consisted of a large water-tight snuff-box, the lid of which was 
held open against a powerful spring by a small wedge that was 
pulled out by the revolving fly-wheel. 
Sir Bobert Christison’s cistern thermometer |] is a water-bottle on 
Hooke’s principle, with unvalved holes below, and carefully adjusted 
ball and cone valves above. 
The water-bottles^f employed on the “Porcupine” and “Light- 
ning” expeditions were valved instruments without a locking 
* Described and figured, Phil. Trans., cix. (1819), p. 208, pi. xi. 
t Described and figured, Nor sice Nordhavs Expedition, iv. pt. 2, p. 17 ; and 
Tornoe’s Chemi (1880), p. 13. 
£ Described and figured in Sigsbee’s Deep-Sea Sounding and Dredging (1880), 
p. 91. § Described, Phil. Trans., cix. (1819), p. 209. 
|| Proc. Roy. Soc. Edin ., vii. (1872), p. 570, and xii. (1885), p. 31. 
IT Depth of the Sea (2nd ed., 1874), p. 500. 
