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Mr. Biram mentions a very simple and linear surfaces, or presenting such angles interesting experiment, by which it may as before specified, are calculated to act be made palpable to ocular observation, with much superior efficiency to all " that vanes or floats having such curvi others." D Fig. 8.
3 “ Let a vessel of water, of any sufficient capacity, be sprinkled over with small bits of paper, or any other light body of about
submerged in it, and moved forward in the floats present at their extremities an direction of its axis ; the wheel will then re angle of about 56°, (those of the two volve freely, but without causing any mate wheels being inclined reverse-wise to rial agitation either in the water or among each other,) and are confined to their the particles floating in it, both of which
position by two ringz upon their periwill remain stationary, those particles of pheries. Each propeller or wheel is onefloating matter only being acted upon which
fourth less in diameter than the ordinary come in contact with the edges of the floats during rotation; showing clearly, that the
paddle-wheel, and only of one-fourth the
width. ". The result of several experiwater produces the rotating action with the least possible disturbance to itself. But let
ments made with these stern propellers, the same experiment be made with a model
says Mr. Biram, "shows that they are, wheel constructed according to any of the
as nearly as may be, of equal power with common plans, with floats having plain sur the common paddle-wheel of larger di. faces, and set in any other position to the mensions, besides possessing the advanline of motion than I have prescribed, there tage of being worked under water, and will then be more or less a surging of the at a part of the vessel where they do not water in front of the wheel, and the floating interfere, as at the sides, with her sailing particles will be more or less agitated and capabilities.” The tremulous motion so tossed about, showing no less clearly, that
often complained of in steam-vessels is the different form and position of the floats also altogether obviated, or nearly so, in has caused an unnecessary obstruction to the
consequence of the oblique manner at passage of the water."
which the paddles enter the water, and Wheels with vanes or floats set at
their reduced number. angles found or determined by the pre In figs. 1 and 2, (see front page,) are ceding rules may be also applied to re given side and end views of a paddlegistering the velocity of bodies propelled wheel to be applied to the sides of vesthrough water, or of the wind.' The
sels, constructed according to the condi. manner of such application Mr. Biram tions before explained. illustrates by a description of the means
" A A are two metal frames, having six to be adopted in the case of registering
arms and two concentric rings, which are the velocity of a vessel at sea ; but the
fastened upon the axles on each side. The details of this we shall for the present arms are fixed in an oblique position with pass over.
regard to each other, those on the reverse In machines which act upon water or side of the wheel being represented by a a. air, instead of the water or air acting B B are six side-plates, which inclose the upon them, and wbich derive their mo wheel on each side between the concentric tion from some other source, as steam rings of the frame, to the extent shown by or animal power, a different principle the shaded parts, and are screwed or riveted from that which has been previously
to the frames A A. The shaded parts reexplained prevails. Mr. Biram examines, presenting the said plates, together with the first, the case of propellers of vessels ap- projecting ends of the paddles marked C, plied at the stern, and rotating in a plane
also show the outline of the paddles when
viewed sideways, as in fig. 1. The paddles perpendicular to the vessel's path.
or floats, CC, which are also screwed or ri. “ Here the useful effect produced by one veted to the frames A A, are placed diarevolution of the wheel may be said to be gonally across the shaded part of the wheel, increased, the more the angles of the vanes and their extremities present an angle of 45° or floats with the plane of motion is in with the side of the wheel, and each point of creased, within certain limits, which may the extremity radiating to the centre of the also be illustrated by reference to figs. 6 and wheel, in lines parallel with the side, so that 7, before described; for if the vanes of the the angle which the paddle makes with the wheel, W, are at an angle of 56}", a cylinder side of the wheel is constantly increasing of air or water will pass through it in one from the extremity inwards, and would be revolution, equal to the depth of the column at the inner ring about 68o. The better to HD; whereas, at 45° only, the depth of the illustrate the form of the wheels, I have said column would be only equal to G D, or given in figs. 3 and 34 diagrams of the side the height of the wheel's circumference." and end views of one of these paddles. In Mr. Biram gives a representation of a
fig. 34, (in which the obliquity of the paddle
is shown the reverse way to that intended to pair of stern propellers constructed according to these conditions, and intended
be represented by figs. 1 and 2,) AB repre- CD to be worked entirely under water. The ing with C D, fig. 3.".
sents the angle at the inner ring, correspond
The form which Mr. Biram recommends for the ventilation of mines is the same as that before described as suitable for stern propellers. The sort of power best adapted to give them the required velocity will, of course, depend on local circumstances; but the following suggestions are thrown out, as generally worth attending to.
“ When applied at the bottom of a shaft, down which there may happen to be a considerable fall of water, I would recommend that the water should be collected in a pipe, and made to impinge on inclined vanes at the extremity of the wheel, (which will give it a great velocity,) but the water vanes must be curved in the opposite direction to the vanes of the ventilator, and at the top
B B side they should be so inclosed as to prevent the air being forced through them, which would have a counteracting effect. When the ventilator is to be fixed at the top of a shaft, it will be found of advantage to have a revolving cap with sails over the pit mouth, on the same principle, exactly, as the selfregulating revolving caps of windmills, and on the sides of this cap, opposite to the wind, to have a circular opening, in which the ventilator may be placed. Such an apparatus would always act well when there was wind; and when the weather was calm, the ventilator might be set in motion by connecting it with a heavy weight, allowed to descend the shaft, and raised from the bottom of it, from time to time, by means of horse, or some other power."
THE BOCCIUS LIGIT. Sir, — With all your professions of im flickering is but concealed from view, partiality respecting the merits of this and not really absent. Neither did new light, it is rather surprising that you Messrs. Brande and Parkes notice it in should pass over, wholly unnoticed, one their Report, even though done to order of its principal recommendations, namely, -we presume, for the same reason. If the absence of all flickering, and the un our correspondent will take a metal cyrivalled steadiness and uniformity of the linder, of a line or two less than the exlight. Can as much be said of any act diameter of the flame of a tallow other ?
candle, and pass it down just over the I am, Sir, yours,
top of the flame, he will find that there
AN OBSERVER. is quite as little flickering visible as in Charing-cross, September 26, 1842.
the case of the Charing-cross phenome
non. Now, this is literally all that Mr. [We did not notice this alleged “ab Boccius has done-all, indeed, that there sence of all flickering," for the best of is new in his most ridiculously-extolled all possible reasons, namely, that the invention.-ED. M, M.]
DESCRIPTIVE NOTICE OF THE GREAT NORTHERN" STEAMER (WITH SCREW
PROPELLER) - AND REPORT OF EXPERIMENTS MADE TO TEST THE DIAGONAL SYSTEM OF PLANKING ON WHICH SHE IS CONSTRUCTED. BY GEORGE BAYLEY, ESQ., MARINE SURVEYOR, LLOYD's.
Sir,— The steam ship, the Great Nor yard of Messrs. W. Coppin and Co. She thern, was launched at Londonderry, Sa is intended to be propelled by Smith's turday the 30th July last, from the ship screw propeller, which is fitted in a space
left for the purpose in the dead-wood cisely the same quantity of materials in abaft. The screw is 11 feet long and each, made from the same plank. 14 feet pitch, and is intended to make Number 1-A model 6 feet long, of 88 revolutions per minute. The screw inches wide, and 91 deep, planked in the is to be driven by a pair of engines of usual mode. the estimated collective power of 360 Number 2-A model of the same di. horses, working at a pressure of 3 lbs. to mensions as Number 1, planked out. the inch.
side in the usual manner. The inside These engines, with their boilers, will planking in two thicknesses, was aroccupy a comparatively small space in ranged so as to form an internal truss, the after part of the hold abaft the main abutting upon shelf or string pieces, and mast, leaving a much larger portion of acting by compression. the ship than usual for the purpose of Number 3-A model of the same dicarrying cargo and passengers.
mensions as the two preceding, and planked The Great Northern will present the outside in the usual manner. The inside external appearance of a large full rigged planking in two thicknesses, was arranged frigate with a flush deck.
so as to act by tension only, being withHer form is calculated for great velo out any abutments. city under canvass, and does great credit The three models were then loaded to the skill of the constructor.
carefully as follows :Without entering into a detailed de
First Experiment. scription of her construction, it may suffice to say, that the frame and out
Number 1-280 lbs., deflected } inch, side planking are arranged in the usual
Number 2—1120 lbs., deflected inch, manner; and that the ceiling, or in
Number 3—2100 lbs., deflected i in. ternal planking, is arranged diagonally
Second Experiment. in two thicknesses from the gunwale to
Number 1-490 lbs., deflected 14 inch, the bilge, where it is connected in a
and appeared to be near the breaking peculiar manner with the thick planks at the bilge. This arrangement is expected
point: on removing the weights, it had
received a permanent set of sth inch. to prevent any alteration of form from the
The other models were not tried with necessarily unequal distribution of the weights on board with reference to the
any greater weights than in the first ex. volume of water displaced at particular
periment; on their removal the models
returned to their original form. parts of the ship. This point has not been generally at
The models were made of yellow pine; tended to in the construction of steam
all fastened in the same manner, with the ships, and the consequence is, that there
same number of wooden pins driven after
an ith inch belt. is scarcely any steamer to be found that does not very soon after being afloat, un
The dimensions of the Great Northern dergo a considerable, and often a very perceptible alteration in her sheer. After the Great Northern was launch
Length between the perpendiculars 2219
37 0 ed, it was ascertained that she had broken her sheer only gths of an inch, instead
Depth in hold
26 5 of several inches, as is frequently the
Tons 1,430 old register measurement.
1,514 new register measurement. case in vessels built in the usual manner.
In order to show the comparative stiff It is estimated that her velocity will be ness and rigidity of his method of build. nine miles an hour, when the screw makes ing, Mr. Coppin furnished the writer eighty-eight revolutions per minute. with three models, of the same length, The following vessels have been already breadth, and depth, and containing pre
built and fitted with the screw propeller.
Ports belonging to.
The following are building :
Ports belonging to. Great Britain
3600 tons 1000 horse
800 tons 200 horse power. .
120 horse power. France. One for ditto
350 horse power. Ditto. Propellers on the same principle have several of the steam vessels built in the been fitted to some other vessels by other Thames had suspension plates introduced parties, with various degrees of success. upon the timbers under the planking. The old river steamer Swiftsure, has This plan was adopted by Messrs. John been fitted with one, and it is said that a Wood and Co., in the Clyde, about the considerable increase of velocity has been same time, they having had particular obtained. Ericsson's 'propeller is sub reference to the unequal distribution of stantially the same in principle, and is the weights in steam vessels, in arrangsaid to answer well. The same remark ing the plates, and succeeded in preventapplies to that patented by Captain Car ing that breaking of the sheer which is penter.
too often seen in steam boats. It is not my intention to trespass upon Mr. Oliver Lang, the talented master your pages by any further remarks, upon shipwright at Woolwich Dockyard, was ihe merits or demerits of the screw pro amongst the first to apply the tenacity of peller, as they have already been brought iron plates to the strengthening our menunder the notice of your readers by gen of-war. So nearly contemporaneous was its tlemen who have devoted much time and adoption in this form to the same purpose attention to the subject.
in naval architecture by different indiviMr. Barlow gives six tons per square duals, that it is difficult to say to whom inch as the ultimate tenacity of yellow the priority belongs.
It is highly propine; whilst a square inch of the same bable, that having their attention called material is crushed by •86 of a ton, or to the defective construction of our ships about one-seventh of the weight. in regard to longitudinal strength, they
Mr. Coppin's plan is by no means new arrived, as they must of necessity have in principle. Some years since a patent done, at the same conclusions as to the was taken out for building vessels with nature and operation of the causes proseveral thicknesses of plank arranged ducing the defect complained of, and apdiagonally; but either from the want of plied the tenacity of iron to remedy it. tact on the part of the patentee, or more Sir Robert Seppings and others had probably, because vessels so built, were
attempted to remedy it by applying the found deficient in transverse strength, power of wood to resist compression, to the plan was not acted upon to any extent. counteract the tendency to hog, or arch. This I think must have been 25 years General Bentham and Mr. Gabriel ago.
About twenty two or three years Snodgrass, were in a certain sense the since Messrs. Tindale of Scarborough, ap predecessors of Sir Robert Seppings in plied diagonal suspension plates upon the the application of timber and iron for inside planking of some vessels built by
this purpose. them, and soon afterwards doubled se
Admiral Chapman, the eminent Swedveral of their vessels with thin planking ish naval architect, in 1767, published in outside, arranged diagonally, so as to act his great work a plan in which the same by tension only; this doubling was found principles of construction are adopted in to add so much to the longitudinal the internal framing of the ship. strength, as almost entirely to prevent In civil architecture, truss framing has any alteration of the sheer, and in po in been long used; but the practical diffistance have I been able to discover any culties in the way of its successful appliindication of straining at the ends of the cation to naval architecture, and perhaps planks.
the prejudice in favour of accustomed Some years since, about 1816 or 1817,
practice, have prevented its general use in that department up to the present
time. • There was a plan for the same purpose, of a much older date than that alluded to by our esteem I am, Sir, yours respectfully, ed correspondent, namely, that of Messrs. St. Barbe
GEORGE BAILEY. and Stuard, the patent for which was taken out
London, September 20, 1842. February 4, 1796,-ED. M. M.