42 On the Depth and Saliness of the Ocean. 
experiment, and how many interesting geological results may be 
elicited and are connected with these experiments ; sufficient facts 
have been developed, to prove that the inequalities of the level 
of the ocean’s bed, are much more remarkable than those of 
the land. 
It may excite pane that we , should know so little on this 
point: navigators, to whom this interesting ees properly be- 
longs, have stowbted themselves little about it, unless it was in 
some way connected with the safety of their that The ex- 
istence of discolored water has alone induced them to cast the 
deep sea lead. There is however some excuse to be made, for 
though in theory the depth is easily to be arrived at, yet to obtain 
it practically is exceedingly troublesome, requiring much time as 
well as favorable opportunities. 
The mode still pranticed is the ordinary lead line. Substitutes 
for this have been attempted; many of them are ingenious and 
me useful, but they re not obviate the difficulties, although they 
give greater accuracy in the results. Few are aware that it re- 
quires from two to three hours for a well appointed vessel to make 
a sounding to the depth of 1500 or 2000 fathoms, for which 
opportunities seldom occur: calms or light winds, and se nema 
; e. 
The mode of sounding practiced of late by availa British offi 
cers to obtain the actual depth, is by attaching a weight of seve- 
ral hundred pounds to a small cord or spun yarn wound on a reel, 
which is carried off as the weight descends ; on reaching the bot- 
tom it is pulled taut and the length ascertained ; the cord being 
too weak to lift the weight, both are lost —consequently, the ex- 
periments are expensive as well as inconvenient to make; the 
time required for the experiments even in this way, is half an ‘hour 
for the descent of the weight; the line in these cases instead of 
being used from the ship, is s lowered from a boat to avoid the drift. 
of the vessel, which is very considerable in the time the weight is 
descending ; ‘this renders the experiment more satisfactory and cor- 
rect. It will thus be seen that it is out of the power of an ordi- 
nary vessel to make the experiments ; in order that this interest- 
ing ent may advance without these difficulties, it becomes 
necessary me new mode of sounding be adopted whereby 
both the siti may be lessened and the opportunities multiplied. 
It has been suggested to obtain an echo from the bed of the 
ocean by the explosion of a shell just beneath the surface, the 
depth to be measured through the propagation of reflected 
The mode which appears to me more Pi i is by the time 
of descent and the direct waves of sound from an explosion at 
some of ie explosive compounds ; the momentum acquired 
eiibio€ the shell wauld enase explosion on s iking th 
