Sibley College Lectures

Chas. T. Porter
1886 Scientific American  
Besides, this can be avoided by closing the lower aperforces, in the sarne plane, or approximately in the same the equilibrium of . instability. It must be rot a ted ture of the tube by a simple plank held with ropes and plane, of revolution. swiftly enough to cause the influence of gravity to by lowering the tube proportionally as it is filled with In the first place, you must understand that the nate disappear, as an element disturbing its position. It concrete, so that the surface of the
more » ... surface of the concrete is always ural tendency of every free revolving body is, to re-will then present an interesting appearance. The line above water. IV-hen the lower part nearly reaches thA vol ve in equilibrium about its center of gravity. The connecting the point of support and the center of bottom, the ropes which support the plank are pulled momenta of all the parts of a free revolving body neces-gravity will become vertical, and form the axis of obliquely, and in this manner remove this kmd of sarily equalize themselves about their common center revolution. The spindle will be inclined from this stopper from the tube. The working is thus begun, of gravity. No matter what the figure of the body may axis, and in revol ving around it, will describe a hollow and no part of the concrete has been weakened. be, nor how irregular its outline, if unconfined it 1'0cone, open at the top,. while the disk will present Owing to the high velocity of the current of the tates about its center of gravity in perfect equilibrium. the appearance represented. In preparing this toy, Loire, we had taken the precaution to ram up-stream a 'rhus, if you pitch a quoit, of any shape whatever, I removed the segment gradually, spinning the top screen of sheeting piles so as to have hardly any cur-giving to it a whirling Illotion, as it flies straight to the after taking off each slice, and was much inter rent in the excavation. W tJ also had everything point at which you really aimed it, although that point ested in ob�erving the enlargement of this cone on in readiness to remove all the soft white marl, but may be far enough from the hub you intended to hit, each successive spinning. The cuts show a plan view this was not required, as the marl did not soften; the it will whirl in equilibrium about its center of gravity. of the t.op and the appearance of the top when spin water was hardly whitened by the lime. Also, when The same is the case in any system of bodies. These, ning, which exhibits very beautifully the tendency of a the foundation of the piers was begun, the concrete however numerous, if free, revolve about their common free body to revolve about its center of gravity. While was laid bare, and we found it very rich and not in the center of gravity. A fine illustration of this is afforded spinning, I mark the spindle near the top with paint. least weakened. The piers of Beuvron, on the same m the case of the earth and the moon. It is commonly When we examine it afterward, we find this paint on line of ROlllorantin to Blois, have been built with the * Continued from page 8472.
doi:10.1038/scientificamerican03131886-8488supp fatcat:u7niqksd7zcw7ms4wbhesny27q