the end I from off the thread, and allows it to be drawn subject only to the permanent tension, and the contact ceases before the operation of drawing up the next loop is begun.

I have called this contrivance the "Thread Stop," because it stops the thread from being pulled off the reel at an inconvenient time.

The application of the thread stop enables the machine to sew over a great variety of thicknesses and of material without trouble. The second improvement has reference to the mode of giving the

causes.

Permanent Tension.

In many machines the tension is given by causing the upper thread to pass over a wheel, having a very acute groove cut in it; this well-known arrangement was adopted in our first machines, and was found to be inconvenient from two The first, that in order to give the wheel a hold of the thread, some preparatory tension is needed, which, on account of its slightness, cannot be regulated with certainty. The second, that the thread is apt to become jammed in the groove, particularly when there are any inequalities on it. To remove these defects, the tension-wheel is laid aside, and the tension is obtained from the pressure of a smooth piece of steel against the thread. The arrangement is sketched in fig. 3. The steel piece on which the stop I presses is continued both ways, the upper part being bent to suit the direction of the thread. At the lower end, a small guiding hole is made, through which the thread is led so as to pass on the inner side of the steel; thence it is guided through a slit made at P, to the outer side of the steel piece, in order to be subjected to the action of the stop I; it then passes along the outer side and through another guiding hole towards G.

The tension is given by the smooth end of the spring NO, which is set so that when in its natural state the end does not touch the thread. In order to bring the end O into contact with the thread, and to press it against the steel plate, the spring is acted on by a spiral wire, capable of being compressed by the regulating nut Q. This arrangement

allows of all gradations of tension, from zero to the highest which is required.

The third improvement is in the arrangement of

The Presser.

It has been usual to fix the foot or presser to a piece which slides in a groove made in the presser-arm, that arm being fixed. The difficulty of adjusting such a slide, so as to move easily, and at the same time to be without lateral shake, is almost insurmountable. By making the presser-arm movable upon two pivots, in the same manner as the needle-arm, smoothness of motion and great steadiness are combined. This arrangement is attended with collateral advantages; the arm may now be made so slim as not to interfere with the view of the work; the motion of the presser almost coincides with the curvature of the needle; and the position of the presser is adjustable.

The fourth and last improvement is in

The Feeder.

The feeder is usually pushed forward by means of a cam and drawn backwards by a spring; the length of the stitch being regulated by arresting the feeder at some part of its backward motion. From this arrangement, it results that the feeder comes suddenly against the detent, and the cam also suddenly against the rubber, thus making two blows for each stitch. One of these is deadened by using a leather cushion, and the other sometimes by using a rubber of wood. These beats are entirely avoided, by causing the cam to actuate one branch of a lever, while the other arm has its length variable. In the actual machine, the first mentioned branch is forked, and takes the cam between its prongs; while the other branch is two-ended. Along this two-ended branch, a small piece, carrying the actuating pin, is made to slide, so as to allow of the feed being nicely graduated; and by passing the actuating pin from one to another side of the fulcrum, the direction of the motion is at once reversed.

The arrangement admits of numbers being struck upon. the arm, whereby to recognise the length of the stitch.

365

Address by the President, GEORGE ROBERTSON, Esq., M. Inst. C.E., F.R.S.E, concluding the Session of 1866-67, at the Meeting 18th November 1867.

GENTLEMEN, I propose this evening, as my contribution to the Presidential Addresses delivered from this chair, to give the Society some idea of what has recently been done in Scotland by civil engineers in the way of marine, hydraulic, and sanitary engineering. To do this with any degree of accuracy, I have had to draw largely on the courtesy of my professional brethren; and I beg to return them my best thanks for the information they have given me. The ground is to a great extent untrodden by any of your former presidents; and I hope the short notices I have to give of recent works, or works in progress, may not be unacceptable to a Society which has on its rolls upwards of fifty members of my own profession.

To commence with the sea, and with our immediate neighbourhood.

The east breakwater which was lately completed at Granton has a total length of 3170 feet. The outer portion, about 1000 feet in length, was made first; the materials for it having been taken over a temporary bridge which crossed the harbour mouth. The re

mainder was commenced from the shore end, and joined on to the outlying portion. This breakwater shelters 53 acres from the north-east wind, making the total area of the harbour 130 acres. A timber wharf, 800 feet in length, has been erected on the west side of the harbour, in immediate connection with the Caledonian Railway, and fitted up with two twenty-ton cranes for shipping coal, and other cranes for general

purposes, all worked by steam. Since the year 1835 the Duke of Buccleuch has expended an aggregate little short of half a million on this munificient private undertaking.

On the opposite side of the Ferry, the North British Railway Company have increased the accommodation for their goods traffic by throwing out a pier to the east of the first one, with a sheltered slip for their waggons to be drawn up from the ferry boat.

The same company are also making a harbour at South Queensferry, consisting of a basin 40 acres in extent, connected with 60 acres of ground for trade purposes. There are to be two piers, one for the passenger traffic across the Queen's-ferry, and the other for the coal and goods traffic. These piers are about 400 yards long, and they are laid out so as to allow engines and trains from the Queensferry Branch to approach all parts of them; the object being to enable large vessels to take in a cargo of coal in twenty-fours hours. The depth along the goods pier is to be 12 feet at low water of spring tides. The quay walls of the piers are designed to give a clear berth, fitted with a steam crane to each vessel, so that it could take advantage of the great depth of water at that part of the Forth, and arrive and depart at any time of the tide.

I have on several occasions described to the Society the various works which have been constructed of late years at Leith by the Commissioners for the Harbour and Docks, and will only, therefore, say that the works connected with the present extension of the docks are far advanced, and are being carried out very much in accordance with the original plan. The trade and prosperity of the port of Leith has increased greatly. The dock revenue has risen, since the opening of the

Victoria Dock, with six feet more water than the old docks, from about L.30,000 to upwards of L.54,000 per annum. The new dock is to be fitted up with Sir William Armstrong's hydraulic machinery for opening the dock gates and lifting the shuttles of the filling culverts. The cranes and capstans round the dock will also be worked by water power. The pressure of the water is obtained, and kept up, by means of steam power applied to pumps, which force the water, at a pressure of as much as 700 lbs. per square inch, through the pipes which convey it to the point of application. The superiority of this system, over steam power applied directly, lies in the concentration of the steam power into one, or more, engines erected in places out of the way of shipping or warehouses, and consequently not likely to expose them to the risk of fire, and in the greater care with which it is managed. The value and economy of the principle consist in a large saving of manual labour, and in the rapidity with which work can be executed.

The system of hydraulic machinery round a dock has, not inaptly, been compared to the circulation of the blood; in which the steam engine represents the heart, the throbbings of which send life and energy through the arteries to the most distant extremity of the body. At Leith the simile will be farther carried out-as fresh water there is precious, a return series of pipes, or veins, will bring back the water which has done its work to the heart, to be again circulated through the system. Most of the docks on the Thames, Mersey, Tyne, Wear, and Humber in England, as well as the Welsh Docks and other places, have this hydraulic machinery; but Leith will be the first port in Scotland to make use of water power as a system.

VOL. VII.

3 B