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oven, built expressly to contain it, and where it will remain for the next two months, which time will be necessary for that gradual cooling process to which it must be subjected. It is fine thing to see a man of Lord Rosse's station, instead of applying a strong mechanical genius, as is often the case, to nicknackeries, at once attacking the most important and arduous problems, and forwarding the highest branches of science. During the very delicate and difficult experiment of yesterday, he was perfectly cool and decisive, and amidst various suggestions from the bystanders, quietly followed his own judgment, which was better than any of them. His present achievement, should it finally prove quite successful, is of the greater value, since the mere expense is quite beyond the reach of an ordinary professional man. This last operation, after having satisfied himself of the manner and practicability of each part of the proceeding, could not have cost him less than £1,000. If the final result proves satisfactory, which there seems no reason to doubt, he will have reached, in the opinion of scientific men, the maximum of effect that is attainable, since the eye, as they atfirm, could not make use of a larger speculum than about 6 feet diameter."

Great Colliery Tunnel.-The Victoria Tunnel, constructed for the conveyance of coals from the Leazes Main Colliery, and Spital Tongues Colliery, to the river Tyne, near the Glass House Bridge, Ouseburn, has been completed, after a labour of two years and ten months. The tunnel, which extends under the Barras Bridge down the Dene, is two miles and a quarter long, and seven feet six inches high ; it has been constructed, at a great expense, by Messrs. Porter and Latimer, the owners of the Leazes Colliery, to enable them to ship their coals on the Tyne. The engineer is Mr. Gilhespie, who has displayed great skill and perseverance in conducting this great undertaking to so successful and satisfactory a termination.- Mlining Journal.

Electric Dyeing.Mr. Baggs has discovered a method of applying the oxides of various metals to the purposes of dyeing cotton cloths by the agency of electricity. He showed, last week, at the Polytechnic Institution, an experiment or two to prove the practicability of his invention.

Experiments with Jeffery's Adhesive Composition. -Amongst the numerous inventions submitted to the Lords Commissioners of the Admiralty, and referred by their Lordships to the Committee of master shipwrights recently sitting at Woolwich dockyard, was a composition to be used in place of the substance with which vessels are at present caulked, to render them water-tight. The experiments ordered to be made by the master shipwrights to ascertain its value when applied to the purpose for which it is intended, and the result, are inter. esting and satisfactory. Two pieces of African teak, a species of wood difficult to be joined together by glue, on account of its oily nature, had a coating of the composition applied to them in a boiling state, and in a short time afterwards bolts and screws were attached to each end, the joined wood placed in the testing frame, and the power of Bramah's hydraulic engine applied to the extent of 19 tons, when the chain broke without the slightest strain being susceptible where the joining took place. A larger chain, of one inch and a half in diameter, was then applied, which broke with a strain of 21 tons, the joint in the wood remaining apparently as firm as at first. The utmost strain the cement can bear in this form, therefore, remains to be proved when experiments are made with larger chains.

Four pieces of hard wood were then joined together, weighing in one piece 44 cwt., and carried to the top of the shears in the dockyard, a height of 76 feet, from which it was precipitated on the bard granite wharf wall below, without any of the joinis yielding in the smallest degree. The result of these severe tests induced the Lords Commissioners of the Admiralty to communicate with LieutenantGeneral Sir George Murray, G.C.B. and G.C.H., for the purpose of making experiments with it in the marshes, by bringing the full force of cannon balls against it. Accordingly, a number of pianks of the 8 inches thick and fir 16 incbes square were joined together with the cement, to represent 8 feet in height and eight feet in length of the side of a first-rate ship of war, without any thing else in the shape of bolt or security to assist the comp«sitica; and it was, on Tuesday, set up as a target at the bat in the marshes. Three new 32-pounder guns were placed at 400 yards distance or point blank range and three shots fired. The effects were wonderfui, lest. ing the wood to pieces, and in only one instance, where the joint had not been good, showing tha: they had any effect upon the cement, so as to rate the joined parts from each other. A bole six iuches and a quarter in diameter was then bored in the centre of the target and a 32-pounder shell icserted, and exploded by a match, which tore the wood to small splinters without in many places in the least separating the composition. This des i vention is said to possess the power of expanding like India rubber in warm climates, and will not be come brittle under the coldest temperature.- Tise.

Magnesian Cement. The valuable properties of magnesia, in the composition of hydraulic ment, were first brought to the notice of the Madras Government by Dr. Macleod, and applied in repara tions of the fort in 1825. About a twelvemonth af terwards, a comparative trial was made betrece a cement of the calcined mineral mixed with sand, a cement of lime and ironstone, and commit chunan plaster, applied to portions of the same wall. After a heavy monsoon the magnesian če ment was found to be the hardest and strongest of the three; and was thought to be fully equal to Parker's cement. The price at which the two cements could be procured at Madras was then equal; but, chiefly in consequence of the discutery of large deposits of the magnesia on the banks of the Cauvery, near Trichinopoly, the magnedan cement can now be produced at less than one-sistä of its cost at that period. A claim to the discovery of this mineral was made a few years ago by Col (now General) Pasley, who was unacquainted with Dr. Macleod's experiments; but on an inrestigation of the matter, made by the authorities in England, the claim of the latter gentleman vas clearly proved, and'a handsome donation of 3400 rupees was made to him by the East India Company. -Lieut. Newbold.

67 Intending Patentees may be supplied gratis with Instructions, by application (postpaid) to Messrs. J. C. Robertson and Co., 166, Fleet-street, by whom is kept the only COMPLETE REGISTRY OF PATENTS EXTANT (from 1617 to the present time). Patents, both British and Foreign, solicited. Specificata uns prepared or revised, and all other Patent ouiness transacted.

LONDON: Edited, Printed, and Published by J. C. Robertson, at the Mechanics' Magazine Office,

No. 166, Fleet-street.---Sold by W. and A. Galignani, Rue Vivienne, Paris;

Machin and Co., Dublin; and W. C. Campbell and Co., Hamburgh.

Mechanics Magazine, MUSEUM, REGISTER, JOURNAL, AND GAZETTE.

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HOLCROFT'S PATENT PORTABLE SAFETY BOAT OR PONTOON. To a people so eminently and essen catastrophe still more frightful to contemtially maritime as the English nation, an plate, namely, the violent ejection or invention which gives additional safety murder of the weakest, in order to lighten to mariners and others, who are led by the overburdened barque—as was seen the necessities or the vicissitudes of life not very long ago in the case of the to traverse the ocean, cannot fail to be American ship William Brown, the regarded with deep interest by the whole crew of which saved themselves in this community.

horrible manner at the expense of the The vast increase that has taken place lives of those whom they were bound to of late years in the numbers of those who protect and to save, even to their own daily seek that occupation and subsistence detriment. in the cultivation of land in the colonies It needs, therefore, no very elaborate which are denied to them on their own exordium to prove that at the present the soil, renders it a matter of the highest principal reliance for the safety of those importance to ensure to them during who “ go down to the deep in ships," is their passage to the distant shores of more in the protection which a gracious Australia or the Canadas, a greater de and ever-merciful Providence is always gree of safety than now unfortunately ready to afford his creatures, and in the has been found to exist ; so that in case goodness of the ship, and skilfulness in of any sudden disaster at sea, and whilst the mariners, than in any hopes of escape distant from any human aid, the mari by means of the boats which are carried ners may be able to command within on board emigrant and merchant vessels. their own vessel the means for ensuring The invention, therefore, of a boat which an escape from the horrors of a death by should combine portability, capacity, drowning, or the still more horrible one lightness of draft, capability of being conof destruction by fire.

tained in a small compass, and unconThe instances, far too numerous to querable buoyancy, and which to those particularise, which are on record of the essential qualities should add that of loss of human life at sea, arising from being economical in its construction, both the destruction of ships by fire or water, in materials and labour,—has long been offer one melancholy reflection to the a desideratum. observer-namely, that the majority of Many persons have obtained patents these fatal occurrences have been the re for inventions within the last fifty years, sult of an insufficiency of boats, wherein purporting to be boats for the preservathe crew and passengers could seek a tion of life in shipwrecks and storms; temporary refuge ; and it has hitherto and the four quarters of the globe have been found totally impossible to remedy furnished those who have engaged in the this evil, inasmuch as the bulkiness and endeavour to construct such a boat, with unaccommodating form of the boats at models of various degrees of merit : but present in use render it a matter of dif hitherto, notwithstanding the numerous ficulty to find safe stowage even for the efforts that have been made, nothing scanty and limited number that are at which can really claim to be successful present to be found on board of merchant has as yet been achieved. The Greenand passenger ships. The consequence lander, the Esquimaux, in common with of this inadequate supply of boats has the fisherman of the Coromandel coast, been, in most cases where the number of have furnished their leathern skiffs, or passengers and crew has exceeded that their fibre-sown massoula boat, as mowhich the boats could contain, to occa dels; and the results, as exhibited in the sion the most awful and desperate strug life-boats of Captains Manby, Basil Hall, gles for priority in obtaining a place in and many others, have been so far good the boats; which has in some cases en that they have replaced the clumsy faded in the swamping of the boats, from brics that were formerly in use for the the multitudes that rushed into them in purposes to which they are applied. Still the hope of escaping death : or else in a there remains to be overcome the hitherto

insuperable difficulty of furnishing a • Patent dated October 28, 1841; Specification

cheap, safe, light and portable boat, which enrolled April 28, 1842.

shall serve the purposes of the mariner

339

HOLCROFT'S PATENT PORTABLE SAFETY BOAT OR PONTOON. whilst engaged on distant voyages, and it becomes a matter of the highest imbe equally at the service of the fresh portance to provide additional means for water sailor, or finally be adapted to the their safe passage across the ocean, or, important services so often required by at all events, for their temporary safety, our troops in the passage of torrents and in case of accident to the vessel which rivers during a march through an un conveys them. The great difficulty in known or hostile country.

the way of providing an adequate number The invention which is now offered to of boats for the safety of crew and pasthe public will, it is hoped, supply the sengers, has hitherto been, as already inlamentable deficiency which is above timated, the unwieldiness and bulkiness shown to exist; and, as the number of of the boats at present in use. There those who seek for food and employment can, according to the present mode of in distant colonies is, owing to the con constructing them, be no more boats car. stant and progressive increase in the po ried in every merchantman than can acpulation, yearly multiplying in numbers, commodate from forty to sixty persons ;

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and even this number would be with vention, but has been patented in this difficulty contained in them, not to speak country as well as in France. It is conof the room required for water and pro- structed upon the principle of a skeleton visions. The number of passengers and frame, easily put together, and as easily crew on board of emigrant ships is fre disconnected and folded in a small comquently double that above mentioned; pass. The skeleton is constructed so as and hence, in cases of shipwreck, foun to fold easily and commodiously into onedering, or other casualties incidental to sixth of the space which it occupies when sea-voyages, there is always a prospect it is expanded and put to its proper use of those horrible struggles for preserva as a boat; and it is covered over with tion amongst the unhappy sufferers which two folds of canvass of the best and have been before referred to.

strongest quality, which, after having The boat in question is of French in been previously prepared with dissolved

caoutchouc, are glued one to the other, made, of their powers of conveying mer. on the inner side of each, by a solution chandise, in the presence of the Minister of of the same material, so as to form an Commerce yesterday, which was also vit. impenetrable and durable covering, wholly nessed by a vast number of spectators. impervious to water, and more capable

“ The first large sized boat of this descrip

tion reached Paris from Auxerre after a of resisting a sudden shock from breakers or sunken rocks, than either oak or

passage of unusual rapidity, and equal free

dom from accidents of every description. the strongest deal planks would be. To provide for the permanent and uncon

Notwithstanding many severe concussions querable buoyancy of the safety-boat, it jected during the passage, —

to which the boat was purposely sub

-notwithstandis provided with air-cells, or cases parti- ing, also, the lack of water, which delayed tioned off, and each rendered independent the passage of other boats on the river ; and of the other, so that in case of an acci.

many other drawbacks, as well studied as dental fissure being made in any one of accidental, — not the slightest injury was these cells, the remainder, being unin sustained by the boat, which preserved its jured, enable the boat to preserve its form, as well as the solidity of its frame, buoyancy.

most perfectly ; nor was there the smallest The strength of the canvass can be in leakage to be perceived. When it is stated creased at pleasure, according to the size that the boat was of the following dimen. of the boat, or the mode in which it is to sions, it will at once be perceived that the be employed, so as to give this material principle upon which it is proposed to cona degree of strength equal to that of sheet

struct them has been subjected to the severest iron; while its pliability adds greatly to

test which could be devised, and that it has the safety of the boat, by enabling it to

endured it with success :- The length of the

boat was 32 metres, 25 centimetres ; the sustain the shock of an accidental encoun

breadth was 5 metres, 10 centimetres. The ter with a rock or other hard body, by

cargo, brought from Auxerre, (in the centre which an ordinary boat would be staved

of Burgundy,) consisted of 17 decasteres of and swamped. The interior of the boat

new wood, weighing 89,862 kilos, (80 tons, may, moreover, be strengthened to any 5 cwt. ;) 4,000 metres of wood in planks, degree required by the employment of weighing 1,8000 kilos, (16 tons, 1 cwt. ;) and thin sheets of iron or planks of wood, several hogsheads of wine, weighing 2,138 disposed so as to form a commodious kilos, (2 tons,) making altogether 110,000 bulwark and footing along the sides and kilos (98 tons, 6 cwt.) of cargo, which was bottom.

safely delivered at the Quai d'Orsay. As Having thus sketched, in a cursory

soon as the cargo was discharged, the boat manner, the advantages and facilities was taken to pieces, (which was effected in which at the first aspect of the invention

three or four minutes' time,) and being placed are suggested to the mind, it may be ad

on two carts, the materials were conveyed visable to examine what has actually been

to Auxerre, to be again put together, and

floated down the stream with another cargo. achieved by the employment of boats

This experiment, therefore, amply testifies constructed upon this principle, of the

to the strength and powers of resistance of materials indicated, in the kingdom of the materials of which these boats are conFrance; and as these facts are on record as structed ; and as their facility of setting up having taken place under the immediate and taking to pieces depends wholly upon their cognisance of the Minister of Commerce, size, it will be found that five minutes, upon the Duke of Orleans, and various other an average, will suffice to ship or unship a persons of the highest rank and of the first boat large enough to carry with ease and intelligence in France, they, perhaps, safety from twenty to forty persons." will serve in some degree as an apology In a mere preliminary sketch such as for what might be said of the capacities this, it is unnecessary to expatiate upon of this patent boat. In the Journal des the numberless ways in which this insenDébáts of April 21, 1841, we find the tion may be turned to account. It offers following description of one of these to those who are fond of aquatic plea

sures a safe and inexpensive means of “We have recently spoken of the new

pursuing their amusements: a folding patent boats, which take to pieces, and are

boat, constructed upon the principle readily constructed, and which were lately herein described, may be carried by one exhibited in minature on the Seine.

man to the water's edge, expanded and “A trial of far greater importance was fitted out in a few minutes' time, and

boats :

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