Description of the Alepus parasita, found in Falmouth.

Vide Polytechnic Report for 1849, page 77.

Body ovate, compressed, covered by a firm cartilaginous sac, semi-pellucid, greyish: the internal membrane reflected on the edges of ventral opening, ciliated, channelled; aperture one fourth the length of sac: cirri slender, short, articulated, hispid,--anteriorly white, posteriorly reddishbrown their motion was slow, but regular. Seminal tube long, slender, curved peduncle short, rather stout, hollow; it contained a jelly-like substance, of a light bluish-white colour. I was unable to detect ovæ, although a very powerful microscope was employed.

Right or Left handed Ratchet-spanner.

BY MR. WILLIAM BOSUSTOW, PERRAN FOUNDRY.

THIS instrument, which is intended for use in cramped or difficult places, where the ordinary spanner is not available, is represented in Plate III., figs. 13 and 14. Inside a fork, at the end of the usual lever, is placed a ratchet wheel, a, shown by dotted lines in fig. 13, and again by fig. 15. This wheel is kept in its position by the studs, b, b, which enter a groove turned in the face of it. It is pierced by a slightly taper hole, which also goes through the forked end of the lever, and is intended to hold chucks of any required shape or size for turning backward or forward the nut or screw which is to be operated upon : different forms for the chucks are represented by figs. 16, 17, 18, the slightly tapering shanks, c, c, being grooved to correspond with the projecting stud, d, on the inside of the ratchet wheel. The ratchet itself, e, which is double and shown by dotted lines in fig. 13, is also placed within the fork of the lever, and may be moved laterally to a small extent round its axis by the spring catch, f, which acts on a V shaped spring, 9, placed between the axis of the catch and the inside of the ratchet. When the catch is in the same direction or parallel with the length of the lever, both of the palls of the ratchet are free from the indented portions of the wheel, which can then turn in either direction; but when the catch is placed obliquely, as in fig. 13, one pall of the ratchet enters one of the indentations of the wheel, which, with its chuck, can then only move in one direction, and thus may be used to turn a nut or

screw.

The catch springs over the projecting pin, h, and is thus held on either side of it, so that the instrument may be used to turn backwards or forwards, or in the right or left direction. The V shaped spring on the inside keeps the ratchet firmly in the indents, and enables the lever to be moved back for a new stroke; the catch being used to bring the right or left side of the V spring into operation, as may be required.

Hand Dibble for sowing Corn or other seed.

BY MR. RICHARD HOSKING, PERRAN FOUNDRY.

THIS machine, see Plate III., fig. 19, is intended to place the seed at such distances that each grain may receive its due share of nourishment, and so as to allow space for cleaning between the sets, while by its use a much less quantity of seed is requisite. The inventor, who has had some experience in agriculture, states that a man can sow half an acre a day with it, and that it causes a saving of four-fifths of the seed. The dibble is held by the handles, a, a, by which it is lifted from the ground; and the seed is placed in the box, b. In lifting it from the ground the plungers, c, c, are partially withdrawn from the tubes or dibbles, d, d, and a communication is opened between the seed on the inside and the dibbles by an arrangement which will be best understood by fig. 20, which represents a section of one of the dibbles, and figs. 21 and 22, which show how the requisite supply of seed is regulated. e and fare zinc plates which slide over one another, e being attached to the part of the instrument which carries the plungers, and consequently moving with them, while f is attached to the box. At the lower part of e is a small slot, g, and a projection or sort of half-cup for taking up one or two seeds, as may be thought best, which are thus carried up from the supply in the box until they reach a small slot in the higher part of f, through which they fall into the tubes and thence into the ground.

When in use the instrument is lifted from and then forced into the ground as far as the lower part of the box, and this action is

continued while the operator walks slowly forward over the ground. In thrusting the tubes into the soil they are necessarily filled with the plungers, but when the instrument is lifted the plungers are first raised and thus allow the seed to fall into the holes they have just left, before the tubes are withdrawn, and the whole machine lifted from the ground; which arrangement ensures the deposition of the seed at the proper depth.

Callipers and Centreing Gauge.

BY MR. SAMUEL MATTHEWS, TRURO.

THE form and construction of this instrument will be readily understood from an inspection of fig. 23, Plate III. It is intended for finding the centre of work which is to be turned, and whenever a centre gauge line is required. It will be found useful to fitters, joiners, and others, as it gives the centre with great accuracy and without loss of time.