. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. Galileo and Leibnitz supposed that the segments of a beam X Y, frac- tured by a weight W, turned about the line A B where the fracture termi- nates But James Bernoulli, Mariotte, and others, were of opinion that the segments had a tendency to turn about a line, as nm, entirely within the section ; the fibres on that side of the line where the fracture begins are extended, and those on the other side compressed. If the beam X Y, resting on two props at X and Y, be fractured by
. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. Galileo and Leibnitz supposed that the segments of a beam X Y, frac- tured by a weight W, turned about the line A B where the fracture termi- nates But James Bernoulli, Mariotte, and others, were of opinion that the segments had a tendency to turn about a line, as nm, entirely within the section ; the fibres on that side of the line where the fracture begins are extended, and those on the other side compressed. If the beam X Y, resting on two props at X and Y, be fractured by the weight W and mn, the line inside of the section A B a 6, about which the segments of the beam have a tendency to turn, then the fibres or filaments in the space „ m 6 a are supposed to be extended, and those in the space B A m n com- pressed. The imaginary line in n, which divides the section A B a 6 into two parU-Ihe area of compression and the area of tension-is called the neutral axis Mr. P. Barlow laboured much to find out the true position of this neutral axis in different sorts of timber. The result of his labours and experiments may be summed up in the following words, the truth of which is very questionable :-" The centre of tension and the centre of compression each coincide with the centre of gravity of its respective area(') and the neutral line which divides the two is so situated, that the area of tension into the distance of its centre of gravity from the neutral axis is to the area of compression into the distance of its centre of gravity from the same line, in a constant ratio for each distinct species of wood, but approximating in all towards the ratio of 3 to ; (?) It would take up too much space to dwell on the absurd conclusions of Mr. Barlow; there are one or two things which require but little consideration to detect, first the neutral fibres do not arrange themselves in a right line in all forms of beams, indeed, if such aline did exist
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