Secondly, a rapid and uniform descent being secured, the indications of a revolving register will be reliable when attached to this plummet; while in the present mode of sounding the slow motion of descent at great depths, renders such a mode of registering the depth uncertain and unreliable.

Thirdly, there being no strain upon the line in the descent and the motion being uniform, it is practicable to determine the depth by the time of descent, making use of a small insulated wire as a sounding line, and determining the instant that the weight strikes the bottom by an electrical signal transmitted through the line. An apparatus was devised as long since as the year 1845, for ascertaining the moment when the weight strikes the bottom, by electricity, but in the mode of sounding heretofore employed, no particular advantage would result from this, while the danger of breaking the electric continuity is very great owing to the strain brought upon the line in the descent; and the plummet as now used descends with such a varying velocity, that even with the time of descent given, no calculation will give the depth. The method has therefore never been put in practice. Whereas, in the method proposed, there is no strain upon the line in its descent, and the plummet will fall through each successive hundred fathoms in the same time; the time of descent will thus furnish a simple means of calculating the depth.

In this process it will not be necessary to recover the line, and the time required to sound the ocean at any point, need only be that required for the plummet to sink to the bottom, moving with any velocity which may be desired.

I have made many experiments on the best method of coiling the line so as to secure its uncoiling with certainty, and without the possibility of strain upon the line, or the occurrence of a kink.

I have also given much attention to the quality and size of line to be used: upon these points, the practical working of the apparatus in a certain degree depends, but being merely mechanical questions they are easily settled. They are fully discussed in the description which accompanies the drawings.

The importance of the problem, which is thus sought to be solved, in connection with the survey of the coast, has never been questioned. A knowledge of the configuration of the bottom of the sea, adjacent to the coast, is necessary to the solution of many questions of importance to navigation, and to science, and especially that of the ruling feature of the Atlantic coast, the Gulf Stream; but besides these considerations the question has become one of great public interest in connection with the laying of submarine telegraphs; the risk of such enterprises being diminished in proportion to the accuracy with which the depth of the sea is known at every point of any proposed

line; and the ultimate practicability of such operations across the Atlantic being yet to be demonstrated by new and more accurate soundings.

DESCRIPTION.

The accompanying plate is a photographic copy of a drawing made from the first instrument constructed. Some slight modifications have since been made in the mode of attaching the register but without affecting the general design.

PLATE I.

Fig. 1. Represents the plummet as it appears in its descent.

T, the tube or case containing the coiled line.

W, the leaden or iron weight inserted in the bottom of the tube.
C, the conical cap.

R, the register in its place upon the cap.

L, the line.

Fig. 1a. Represents a longitudinal section of the tube, weight and cap; showing the mode of coiling the line in balls, and the small specimenbox s passing through the hollow weight.

Fig. 2. Represents the register on a larger scale.

hh, the helices or blades.

rr, the register wheels.

gg, the locks for gearing and ungearing the wheels.

Fig. 2 a, represents the plan or horizontal view of the register, it being constructed so as to offer the least resistance in passing through the water. Fig. 3, shows the detailed construction of the register wheels, and the helices.

From fig. 1, it will be seen that the form of the apparatus admits of rapid motion through the water. The weight is conical and elongated and the register presents the edges only, of brass plates to the water, and the line being uncoiled and discharged from the tube, there is no retarding force to the descent, from the line itself. Any desired velocity of desent may be given to the plummet by increasing or decreasing the weight W.

Fig. 1a, shows the method of coiling the line.

There are various modes of doing this which are in common practice in twine and cotton factories; that which is here exhibited is the method of coiling in balls; all the balls exhibited in the tube being formed of one unbroken line, the line drawing out from the centre of each, until it is all drawn from the tube. The machinery for winding these balls is very simple; a drawing of that which I have used is herewith enclosed.

The essential points in the coiling are to coil the line in as compact a space as possible, and so as to ensure a certainty of discharge without danger of kinking. Two other modes of coiling are now under consideration, either of which may be better than the method by balls. One is to wind upon a spindle, and the other to lay the line in a sort of compound coil, directly in the tube. All these methods are now practised in the factories on a large scale, for winding twine and cotton.

The line used should be about five hundredths of an inch in diameter and as strong as it can be made of that size. A braided line of Holland

flax, or silk of five hundredths of an inch in diameter, may be made to bear a strain of 40 or 50 lbs.; which is abundantly strong for the purpose, as the weight and case are left at the bottom, the register and specimen tube only being brought up.

Tube.-The tube may be made of tin in sections of eighteen inches length, with stove-pipe joints and bayonet fastenings. The object of this is to adapt the length of the tube readily to the amount of line which it is to contain. A tube four inches in diameter will contain nearly a mile of line to each foot of the tube.

Sinker and Specimen-tube.-The sinker is made of cast iron or lead of any desired weight, depending upon the desired velocity of descent. A weight of 25 lbs. has been adopted. The sinker is conical and is inserted into the lower end of the tube containing the line and fastened to this tube by screws or by a bayonet joint and fastening. The weight has a conical hole or cavity through its entire length, through which the small specimen-tube passes in the manner shown in the drawing. The specimen-tube is a tube of thin brass passing through the weight and attached to the lower end of the line within the large tube. This specimen-tube is fitted with a valve opening upwards in the bottom, which closes when the tube is drawn up, thus retaining the mud which is forced into the tube when the weight strikes bottom. The specimen-tube fits loosely in the hollow of the weight, so that it may be easily drawn out as the line is hauled in.

Cap.-The cap is used for two purposes; to contract the upper end of the tube containing the line, so that the line cannot rise in bulk out of the tube, and for supporting the register. It is formed in the shape of the frustum of a cone, cut away on one side as well as open at the top, so as to allow the line to be discharged freely. A flat strap is fastened to the top of the frustum nearly in the line of the axis of the tube, and upon this strap the register is set as shown in the drawing; the register is kept in its place by loose collars.

Register. The apparatus for measuring the depth consists of a helix or curved blade attached to a vertical axis, and wheels gearing into an endless screw upon this axis. The revolutions of the helix caused by the motion through the water are communicated to the wheels which are graduated so as to indicate the number of revolutions of the helix.

Two registers are attached to one plummet by attaching them together in the manner shown in fig. 2, by means of brass plates. The blades are made to turn in opposite directions and will operate as checks upon each other, and also counteract the effect of any rotary motion in the plummet. The construction of the blades and wheels and the mode of gearing them with the endless screw are shown in fig. 3. The wheels are differential wheels, that is, they are concentric, one of them having one hundred teeth, and the other one hundred and one teeth. The cross-bar (b) has a slight motion carrying with it the wheels; this motion is governed by a spring s. To gear the wheels, the cross-bar is pressed towards the endless screw until the teeth gear with that screw and the bar is there locked, as shown in fig. 2, at g g. The revolution of the blade will now cause both wheels to turn, and after one hundred revolutions the wheels will be found separated by one tooth or one division. The differences thus measure hundreds of revolutions.

In the register from which the drawings were made, the blades revolve once in two feet; one hundred revolutions will therefore correspond to two hundred feet, or one division of the scale of the register to thirtythree fathoms.

When the register is hauled up, the arms at gg, fig. 2, drop, and the springs cause the wheels to ungear and fly back, where they are held motionless by a projecting point at n, fig. 3. The arms are made to drop by means of a small wire which is attached to the cap as shown at u fig. 1; this wire is fastened to, or hooks over the ends of the arms, and when the register is drawn off, the arms fall.

Mode of attaching the line to the register and specimen-tube.-Before the line is put into the tube it is attached to the specimen-tube at a point four or five feet from the end of the line, the spare end is passed through the tube, and when the balls are all put in the tube the extreme end of the line coming out at top is attached to the register, after taking a few turns round the top of the strap, the register being in its place.

The line is thus attached to the register and specimen-tube only, and not to the large tube or weight. When the plummet strikes the bottom a part of the line will remain in the tube coiled; by hauling in the line this part will however be uncoiled, and on coming to the bottom of the coil, the specimen-tube will be drawn up through the large tube, and after the specimen-tube comes out the register will be drawn off the strap, and thus the large tube and weight will be disengaged from the line, specimen-tube, and register; and by continuing to haul in, the register and specimen-tube will be brought to the surface.

The plummet on striking will, under most circumstances, remain sticking in the mud in an upright position.

ART. II.-Notice of New Localities, and interesting varieties of Minerals, in the Lake Superior region: supplementary to the chapter on this subject, in Part II. of the Report of Foster and Whitney; by J. D. WHITNEY.

SINCE the publication of the second part of our "Report on the Geology of the Lake Superior Land District," in 1851, some materials, illustrative of the mineralogy of this region, have accumulated in my note-books, which, in the present communication, I have put together in the alphabetical order of the minerals noticed, for convenient reference. A few of the facts here stated were communicated to J. D. Dana, for the last edition of his "System of Mineralogy," and are here repeated, with some additional remarks on the general mode of occurrence or econom. ical importance of the ores and minerals mentioned.

Analcime. This mineral is quite abundant on Keweenaw Point, and has also been noticed by me on Michipicoten Island; it does not appear to have been observed in the Ontonagon region. The finest locality, however, by far, is at the Copper Falls

and Northwestern mines; and, especially, at the last-named place, where work is, for the present, suspended. Both these mines are, in fact, on the same vein, the Copper Falls mine being to the north, and the Northwestern to the south of the great belt of crystalline, unproductive trap, which runs through the middle of Keweenaw Point. In this vein, analcime occurs in large and almost transparent crystals forming geodes in the greenish magnesian silicate which is the principal gangue of the vein. These crystals are all trapezohedrons, and sometimes occur an inch in diameter; they occasionally have a thin incrustation of chrysocolla. The analcime, at this locality, is almost always associated with the peculiar form of orthoclase, so common in the copper region, and which will be noticed farther on.

At the Old Copper Falls vein analcime has been found in radiated-fibrous as well as granular-massive forms, and of a bright red color.

Apophyllite.-The foliated variety, or ichthyophthalmite, was found in great abundance in 1853 in the rubbish thrown out at the workings on the Prince vein, on the north shore. A variety in small, brilliant, deep-red crystalline scales or spangles, disseminated through calcite, forms curious and elegant specimens. The most usual occurrence of apophyllite at this locality is in large contorted plates, somewhat resembling the variety of calcite known as argentine. Crystalline specimens are occasionally met with at the Cliff mine, but none have been noticed in the Ontonagon district.

Barytes. There are numerous veins of sulphate of baryta on the north shore of the Lake, and especially along that portion lying to the north west of Isle Royale, as also on that island, and the smaller ones which lie near the main land to the westward of Thunder Bay. These veins vary in width from a few inches to several feet, and are usually made up of quite compact barytes without crystallization, and destitute of accompanying metallif

erous ores.

The famous "Prince vein," on Spar Island, is one of the most conspicuous and interesting objects, at least in the eye of the mineralogist, in this region. As it makes its appearance on the south side of the island, on the precipitous face of the trap cliffs, which rise nearly vertically from the water, it may be seen from a distance of several miles out on the lake; and when shone upon by the sun, resembles a magnificent waterfall, its brilliant white contrasting strongly with the dark color of the trappean rocks in which it is enclosed.

The course of this vein is about N. 32° W., or nearly at right angles to the general trend of the coast of this portion of the lake. At the southern edge of Spar Island it is fourteen feet

SECOND SERIES, VOL. XXVIII, No. 82.-JULY, 1859.