Item 90 - Letter from Eaton Hodgkinson

Pendleton, Manchester - Thanks WW for the present of his work and on looking over his paper on impact, EH offers a further explanation concerning his method used 'in seeking by an approximate mode for the inertia of the bar'. He is trying to find a near value of the inertia of a beam on impact: 'The inertia, I presume depends on the form of the curve, and its strict determination is above my feeble powers. The curve from impact is obviously in some degree serpentine, particularly where the beam is struck toward the ends. This was mentioned to me by Sir John Herschel at Cambridge. I had not however been able to discover any undulations in the form of the curve, under the small impacts in my experiments. The subject of impact I hope to inquire further into, but I feel I must skim upon the surface for want of more mathematical knowledge. Poisson I have heard has something fresh in the 2nd edition of his mechanics - I must get it'. WW expressed a wish to use some of EH's work on Beams and Chain Bridges in the new edition of his Treatise on Mechanics and he is welcome to do so. The paper on the performance of steam engines was a private communication to one of the secretaries to the Philosophical Society [Manchester], and is by an engineer called Edward Dixon, who is in the office with his brother the engineer of the Manchester end of the railway. They are willing to give as much information as they can: 'The short paper alluded to commences with a definition of 'Horse Power' as applied to Engines - shews the superiority of Engines over horses on Railways gives the amount of friction on them - and some calculations and facts as to the power of Engines to take loads up the small inclinations. The paper when modified and improved by the author, and some additional facts are added to it, will be sent to you to use what you please of it'.