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The principal spans cover a length of about 1,150 feet. It will be seen from the diagram that there is a difference of nearly 100 feet in the levels of high and low water. M. Tresca has contributed to the Comptes Rendus some observations on the effect of hammering, and the variation of the limit of elasticity of metals and materials used in the arts.
Necessity of avoiding these at Paris. Membership of the upper jury. Meissonier. Tresca. Jules Simon. Wischniegradsky. Difficulty regarding the Edison exhibit. My social life in Paris. The sculptor Story and Judge Daly. A Swiss-American juryman's efforts to secure the Legion of Honor. A Fourth of July jubilation; light thrown by it on the ``Temperance Question. Henri Martin.
This is no doubt due to the fact that the heat is then conducted away more rapidly. On the whole, the results are summed up by M. Tresca as follows: The development of heat depends on the form of the faces and the energy of the blow. In the case of faces with sharp edges, the process described allows this heat to be clearly indicated.
M. Tresca also protests against the elongation of metals under breaking strain tests being stated as a percentage of the length. The elongation is in all cases, chiefly local; and is therefore the same for a test piece 12 inches or 8 inches long, being confined to the immediate vicinity of the point of rupture.
Tresca, at the Paris Exhibition of 1867, the gas consumed was 44 cubic feet per indicated horse power per hour. According to tests I have made myself in Manchester with a two horse power engine, Otto and Langen's free piston engine consumes 40 cubic feet per I.H.P. per hour. This is less than one-half of the gas used by the Hugon engine for one horse power.
Tresca showed long ago that internal friction is not infinite in a solid; certain bodies can, so to speak, at once flow and be moulded. M.W. Spring has given many examples of such phenomena.
But let us look at the other side also. Does science owe nothing to art? Only a short time since the illustrious French physicist, M. Tresca, was enumerating the various sources of loss in the transmission of power by electricity along a fixed wire, as elucidated in the careful and elaborate experiments inaugurated by M. Marcel Deprez, and subsequently continued by himself.
After giving diagrams and tables to illustrate the geometrical disposition of the areas of fusion, Tresca feels justified in concluding that the development of heat depends upon the form of the faces and the intensity of the shock; that the points of greatest heat correspond to the points of greatest flow of the metal, and that this flow is really the mechanical phenomenon which gives rise to the calorific phenomenon; that for action sufficiently energetic and for bars of sufficient dimensions, about 0.8 of the labor expended on the blow may be found again in the heat; that the figures formed in the melted wax for shocks of less intensity furnish a kind of diagram of the distribution of the heat and of the deformation in the interior of the bar, but that the calculation of the coefficient of efficiency does not yield satisfactory results in the case of moderate blows.
"The population of the West Indies," adds Sir A. Musgrave, "is now greater than that of any of the larger Australian colonies, and three times that of New Zealand." M. Tresca has lately presented to the Academy of Sciences some very interesting experiments on the development and distribution of heat produced by a blow of the steam hammer in the process of forging.
Tresca, and had been communicated a fortnight ago to the French Academy of Sciences. Taking the relative conductivity of iron wire employed by Deprez, and the 3 in. rod proposed by the lecturer, the amount of power that could be transmitted through the latter would be about 4,000 horse power.
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