Lectures on natural philosophy the result of many years' practical experience of the facts elucidated. With an appendix: containing, a great number and variety of astronomical and geographical problems. Also some useful tables, and a comprehensive vocabulary / [Margaret Bryan].

  • Bryan, Margaret, active 1815.
Date:
1806
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on natural philosophy the result of many years' practical experience of the facts elucidated. With an appendix: containing, a great number and variety of astronomical and geographical problems. Also some useful tables, and a comprehensive vocabulary / [Margaret Bryan]. Source: Wellcome Collection.

    102/510 (page 46)
    If one man be twice as strong as the other, the weight should be moved towards the stronger man in that proportion, namely, to half the distance from the latter that it is from the former; by which means the weaker man will bear only one-third of the burthen. In attaching a ])air of horses to a carriage, if one be weaker than the other, the stronger horse should be placed nearer the centre of the beam, that is fastened to the carriage, than the weaker, by which means each will draw in proportion to its strength; the motion of the carriage will also be facilitated by tliis equipoise of power. AVe may infer from the direction of power in horses, that they were designed to draw burthens; and may suppose that a horse will draw a weight in proportion to his strength; yet it is easy to under- stand, from our observations on action and reaction, that two horses of unequal strength may draw the same weight; or the weaker horse may even draw a weight the stronger cannot remove, if the weaker be the heavier, or exceed the other more in weight than he is ex- ceeded by him in strength; for a weight reacts and pulls back a horse in pn>portion to itself; therefore the heavier horse, though he be the weaker, will, if his weight be greater than the strength of his antagonist, lose less power than the stronger one. A horse has two sources of power in drawing weights : his strength, Avhich gives him velocity : and his weight, which gives him force. Horses must have sufficient force or weight to enable them to move a heavy carriage; for if they have not, they cannot secure their feet on the ground, but will slip, and be drawn backwards. In ancient times sledges w'ere used to convey heavy goods; but since the power of wheels has been ascertained, they have been adopted, as better calculated to overcome obstacles and diminish weight; for a wheel turning on an axis, diminishes the resistance.