SOUNDINGS, DEEP SEA. 



SOUNDINGS, DEEP SEA. 



682 



experience gained iu them led to various contrivances whereby the 

 saving of the line at the expense of the shot might be effected. In 

 the Dolphin, U.S.N., an improvement was made in having shot so cast 

 as to slide upon an iron rod. Upon the latter touching the bottom, the 

 shot released itself, and the line and rod were more easily recovered. 

 A great advantage over the rod and shot wa<! gained by the inven- 



Jtalt 



jl.Fuct. 



tion of a kind of double claw, acting somewhat upon the principle of 

 that used for detaching the monkey of a pile-driving machine. It was 

 invented by a blacksmith of H.M.S. Spitfire in 1851, named Carmelo 



Bonnici, a Maltese. Captain Spratt, R.N., who commanded the 

 Spitfire, introduced it to public notice in the 'Nautical Magazine' 

 for 1856. 



As the increasing demand for submarine telegraphs will much extend 

 the work of deep-sea sounding, we give a few diagrams of the means 

 employed in that interesting operation, as well as some sections of the 

 sea bed, carefully drawn to a scale, and, in order to facilitate com- 

 parisons, each of them has the horizontal scale in proportion to the 

 vertical as 30 to 1. 



Bonnici's claw, as it is called, consists of two metal hooks of peculiar 

 shape working on a pin, so that on any weight being attached it 

 clasps and sustains a wire or line ; its great advantage being that any 

 kind of sinker may be used with it, namely, either a shot or a pig of 

 iron, or, on the want of these, a piece of heavy stone. In the above 

 figures, No. 1 shows the outline of the apparatus when in course of 

 descent, a a being the claws hooked into a rope-grummet, c, suspend- 

 ing a weight, b ; the arms, d d, of the claws lie close to the link e, to 

 which is fastened the sounding-line /, and the whole outline is such as 

 to favour the descent of the apparatus ; but the moment the lower 

 portion touches the bottom, the arms d d being relieved of the weight 

 of the sinker, drop, as in fig. 2, and the claws detach themselves from 

 the grummet, and the weight is left at the bottom. 



It will be noticed that a piece projects beyond the underpart of the 

 sinker which, among various contrivances, is loosely tied with string, g, 

 to the body of the sinker : this has a hollow armed with tallow in the 

 end, to bring up indications of the nature of the bottom bed, as in the 

 ordinary hand-lead. On the sinker being detached from the apparatus, 

 a small string, h, attached to the link of the instrument draws this 

 clear of the mass of the sinker, and it is hauled up with the line. 



This was a great step towards a better system, but it required con- 

 siderable care in setting the instrument, so as to insure the ready 

 detachment of the weight on reaching the sea-bottom. Captain Spratt, 

 however, made excellent use of it. He was engaged in sounding upon 

 an extensive scale in the Mediterranean. In the accompanying section 

 it will be seen that his greatest depth was 2170 fathoms, or nearly 2J 

 miles : this was obtained iu about lat. 35 30' N., and long. 18 45' E. 

 It shows that eastward of Malta there exists a small plateau, having 

 on it from 70 to 80 fathoms water, but that 50 or 60 miles from Malta, 

 in the same direction, there is an enormous submarine escarpment of 

 some 2000 fathoms, or 2J English miles. 



Section 1 . 



Caiulta or Crett. 



TnnU to Candia or Crete. 



Scale Horizontal 130,000 fathoms ) . 



Vertical 4,533 ] to one inch, or SO to 1. 



In the following section we see that the bed of the Mediterranean I (after passing the deeps about Candia) being 420 fathoms, and then 

 rises u we proceed northward in the Archipelago, the deepest water | gradually shallowing. 



Section 2. 



1 I 



'! o o 



< 5 O O .-.CIOO O r. O O O 



** ^t o e -r oo e-t I- i n_ 



O > i - 'r r i -. i C i /- i - : j 



I I 



a 2 



o o o o o o o oo o o o o 



rf> ei o ?< -o -* c* to oo oo oo o vcitoio oo 

 MCCI oo ^-^^^ eo^< 



Candia, or Crete, to Teuedo. 



In 1857, Captain T. Mansell, in H.M.S. Tartarus, wag occupied in 

 sounding between Alexandria, Rhodes, and Smyrna. He also used 

 lionnici's claw, but had in addition Lieutenant Brooke's (U.S.N.) appa- 

 ratu* in which had been substituted a conical mass of iron, sliding on 

 a rod. This is an exceedingly simple and ingenious plan, but has been 

 mirpaajed by improvements yet to be described. Captain Mansell 

 seems to have given each of these instruments a fair trial in the 

 Mediterranean, and records his decided preference for the Bonnici 

 < 1 iw. The following will explain Brooke's apparatus. It is remark- 

 able as the one used in discovering the plateau existing between Ireland 

 and Newfoundland. 



In fy. 3 (col. 683), a a are arms working loosely upon a pin at I, con- 

 necting them with the rod c. The sounding line is attached at d to the 

 bridle connecting the upper ends of the two arms. The conical weight 



Scale Horizontal 60,000 fathoms 



Vertical 



2,000 



to one inch, or 30 to 1. 



sliding upon the bar, is held in its position during the operation cf 

 sounding by a looped line passing under the base of the cone, and 

 loosely hung on the spurs, e e, of the arms ; immediately on the sound- 

 ing-line being relieved of the weight of the apparatus by the latter 

 touching the ground, the arms drop into the position shown by dotted 

 lines, and the loops slip off the spurs, thus detaching the cone altogether, 

 which slips off the bar. But here is supposed to be a defect in the 

 apparatus, inasmuch as the force necessary to draw the rod from the 

 aperture of the cone, when in a much inclined position upon rocky 

 bottom, is found enough to break the line at great depths. 



Another excellent form of simple apparatus was invented by 

 Mr. Skead, R.N., Master of H.M.S. Tartarus, and found by 

 Captain Spratt to answer admirably in comparatively shallow water. 

 Fvj. 4, is a sketch of it. The sounding-line is attached to a small metal 



