the momentum of the moving power. The remainder serves to raise a weight of twelve pounds with a uniform velocity of an inch in a second: that is to say, the machine continually winds up itself, and leaves a disposable power, equal to four times what would be necessary in an external agent to keep the machine in motion. It follows from what has been said, that, in the machine of Mr. Cagniard, the heat at least quintuples the volume of air employed in it; since it is evident, that the effect produced must be proportional to the volume of this air dilated. I have said at least, on account of the friction to be over- The friction come: but this friction is very trifling, because both the very triding, screw and the wheel, being immersed in water, lose a considerable portion of their weight, and consequently press very little on their pivots. Besides, the movements are slow, and not alternative, and there is no jerk in them; so that this machine is free from those resistances, that commonly con- and wear but sume great part of the moving power in others, and accele- small. rate their wear. We do not look upon the machine of Mr. Cagniard as It may be useful in practice an object of curiosity merely: it may be useful under in various situvarious circumstances. As it produces its effect in a body ations. of water heated only to 75° [167°F.], or even less, it affords an opportunity of turning to account the hot water, that in various manufactories is thrown away, or runs to waste. In saltworks, for instance, the ebullition of the saline solution might be made, by means of Mr. Cagniard's machine, to work the pumps for filling the boilers: in ironworks the heat of the furnace might be made to work the bellows: in common steam-engines, which, like that at Chaillot, furnish a large quantity of very hot water, an action might be obtained equivalent to that of several men, or horses: in fine, in baths, distilleries, potteries, limekilns, glasshouses, founderies, and wherever there is a production of hot water, or of heat, advantage might be made of Mr. Cagniard's machine. This machine, which, as has been said, is liable to very little friction or want of repair, has also the advantage of being easily managed; and when its action is suspended for a time without extinguishing the fire, the heat is not VOL. XXIX.-JULY, 1811. lost; N The screw of Archimedes may be used lost: for, as the water is not boiling, the heat accumulates in it, and furnishes afterward a more powerful action. The screw of Archimedes, employed in' this machine, produces the effect of a pair of bellows, and might be used in this way for as such in a foundery. It may even be considered as the blowing large best that is known, not only from its simplicity, solidity, fires with great advantage. and constant action, but from the saving of power in its use compared with any other machine employed for the purpose; for the screw becomes very light and very movable by its immersion in water, so that the friction of its pivots is next to nothing. The machine applicable to raising water by means of mercury. General report. Mr. Cagniard has likewise applied the action of this machine to a body of mercury. As its mechanism requires two fluids of unequal densities, he has merely substituted mercury for water, and water for air, retaining the same construction as is mentioned above. The result is a very simple hydranlic machine, which, without valve, stoppage, or action of fire, being set in motion by any external agent, as a man or a stream of water, gives a continual flow of water at a height fourteen times as great as that of the column of mercury, in which the screw is immersed. This height may even be increased at pleasure, without altering that of the mercury, by combining the action of three fluids, mercury, water, and air. For this purpose, instead of raising a column of water alone a lighter column is formed by a mixture of water and air. This mixture is effected of itself, by disposing the lower part of the pipe that contains this column so as to leave its opening partly in water, partly in air, according as we would have more of one fluid than of the other, and consequently occasion the rise of the mixture to a greater or less height. It is obvious however, that this does not alter the momentum of the moving power, but that, when we would raise the water to a greater height, the machine yields a proportionally smaller quantity. This effect is analogous to that of the Seville pump. The machine of Mr. Cagniard appears to us to include many new and ingenious ideas. Its application has been guided by sound theory and a thorough knowledge of the true laws of physics. It appears to us, that it may be useful to the arts on various occasions. We think therefore, that that the author merits the encouragement of the class, and propose, that its approbation should be given to the machine. IV. Description of an Instrument for facilitating the Reduction of Plans; by Mr. DE LA CHABEAUSSIERE. I HAVE thought of an instrument for reducing plans, Simple instru which is so simple, that I am surprised it was not invented by others long ago: but this simplicity, which I consider as an advantage, is probably the reason. I call it a minudometer, as its principal object is the reduction of plans; though it will answer equally well for enlarging them. ment for re ducing plans. scribed. This instrument is a wooden rule, with fiducial edges, at The minudothe extremity of which is a pivot; or a plate of metal with a meter dehole, into which a pivot may be inserted at pleasure. This pivot is a piece of a needle, with a knob for a head. plans of mines. On this rule are marked two scales, one smaller than the other in any proportion you please. As my purpose in making it was chiefly for plans of nines, I took as a basis a Particularly scale of 3 lines to a fathom, the proportion generally used adapted to for such plans; and for the reduction I employed a scale of one line to a fathom. Such a scale diminishing the length and breadth of a plan two thirds each; all the parts will be brought sufficiently near to be considered at one view. Such a plan may be inferior in minuteness of detail and accuracy to a larger, but it has the advantage of being more portable, and will enable the manager to have a clear idea of the works under his direction. Suppose then I would reduce a plan of three lines to the fathom to a third of this in all its dimensions. I take a rule of two feet long, which appears to me the most suitable length, and divide it into three parts, which makes eight inches, or 96 lines [of course in English measure 80 lines] to each part. On the first division, reckoning from the pivot, I trace the little scale of one line to a fathom, which gives me 96. From the extremity of the small scale I begin the division • Journal des Mines, Vol. XXVI, p. 461. Extracted from a paper sent to the Council of Mines. N2 Method of making the instrument, and using it. A different construction. of the larger, and the 192 lines remaining give me 64 fathoms each represented by 3 lines*. I afterward subdivide each of these scales by three. I fix together the plan and the paper on which it is to be reduced, the latter being under the small scale; and place the rule so that it can traverse circularly as much of the large plan as its extent will admit. The rule being fixed on the large plan wherever it touches a point to be transferred to the paper, I note the number of toises on the large scale, and opposite the same number of toises on the small scale I make a mark with the point of a needle set in a handle, or merely with a fine lead pencil. Thus I set down all the parts of the plan one after another, which are found just and in due proportion. If the plan to be reduced exceed the length of the rule, the instrument may be removed to another place. I need not mention the necessary precautions in this case for placing the minudometer properlyt. At first I placed my pivot between the two scales, counting the divisions in opposite directions; but as the plan was reversed in this case, I had not the advantage of comparing it readily with the original as I proceeded. It is obvious, that, if we would have other divisions, we must have different rules, or trace these divisions on paper, and paste it on the same rule. The rule may be graduated also on both sidest. V. It might be supposed from the tt, that Mr. de la Chabeaussiére began to count the divisions of the large scale from this point; but this would be obviously wrong: both scales must begin their count from the pivot, consequently the first division in the larger scale must be reckoned, in the instance before us, as 33, so that both scales will end with 96. It should have been said too, that the pivot, or the hole for it, must be placed in a line with the edge of the scale carrying the divisions. C. Though the divisions of the scale amount to 96 toises, there are only 64 that can in reality be used. Consequently it must be necessary to shift the minudometer and the paper once at least. C. If the edges were bevilled in opposite directions, and the rule were in two parts, made to fit into each other either way where the smaller scale terminates; and the units were of different lengths, though similarly divided; this would give four proportions for diminishing or enlarging. If for instance the principal divisions of one of the large scales were an inch, and V. On Mortars and Cements; Experiments that show the Cole- HAVING sand. AVING found, that an alkaline lixivial gas was evolved Gas evolved from a mixture of three parts of sand and two of lime slacked from lime and by immersion; and desirous of ascertaining, whether the products of the three kingdoms, mingled in the same proportions, would afford a similar gas; Mr. Sage made a number of experiments, which taught him, that the force of cohesion contracted by slacked lime was greater with metallic Metallic oxides strengthen oxides in general, than with any other substance. These trials led him to new facts, which enabled him to discover mortars, or cements, at least as solid and impermeable as those made with the best puzzolana, which is of the greatest use, particularly in hydraulic structures. The work we announce points out also a prompt and easy method of ascertaining the solidity and impermeability of mortars or cements, which cannot but be highly interesting to builders. mortar, in the air may not stand We must not always judge of the goodness of a cement Mortar solid from its having acquired a great deal of solidity in the open air, for it frequently loses this in water, in which it diffuses water. itself. Buildings made with such mortar soon tumble to pieces. tar. The necessity of a minute division of the substances, that enter into a cement, cannot be insisted on too strongly. Rules for making good morThey should first be mixed together uniformly while dry; and they must not be drowned in water, which must be added gradually, till the mixture is reduced to a soft paste. and of the other an inch and half; and those of the small scales, one half an inch, the other a quarter; we should get the proportions of a half, a third, a fourth, and a sixth. Two rules, with joints mutually fitting each other, would give 16 different proportions. If both edges be graduated, there must of course be a hole for a pivot at the extremity of each. C. • Journal des Mines, vol. XXVI, p. 471. The above appears to be the title of a pamphlet, which Mr. Sage has published separately. |