A Treatise on the Theory of Screws

APPENDIX II. 497 the committee, but his antiquated tactics were quite out-manoeuvred by those of Helix and One-to-One. I need only mention two more names. Mr Commonsense was, of course, present as an ex-officio member, and valuable service was rendered even by Mr Querulous, who objected at first to serve on the committee at all. He said that the inquiry was all nonsense, because everybody knew as much as they wished to know about the dynamics of a rigid body. The subject was as old as the hills, and had all been settled long ago. He was persuaded, however, to look in occasionally. It will appear that a remarkable result of the labours of the committee was the conversion of Mr Querulous himself. The committee assembled in the presence of the rigid body to commence their memorable labours. There was the body at rest, a huge amorphous mass, with no regularity in its shape—no uniformity in its texture. But what chiefly alarmed the committee was the bewildering nature of the constraints by which the move- ments of the body were hampered. They had been accustomed to nice mechanical problems, in which a smooth body lay on a smooth table, or a wheel rotated on an axle, or a body rotated around a point. In all these cases the constraints were of a simple character, and the possible movements of the body were obvious. But the constraints in the present case were of puzzling complexity. There were cords and links, moving axes, surfaces with which the body lay in contact, and many other geometrical constraints. Experience of ordinary problems in mechanics would be of little avail. In fact, the chairman truly appreciated the situation when he said, that the constraints were of a perfectly general type. In the dismay with which this announcement was received Mr Coimnonsense advanced to the body and tried whether it could move at all. Yes, it was obvious that in some ways the body could be moved. Then said Commonsense, ‘Ought we not first to study carefully the nature of the freedom which the body possesses ? Ought we not to make an inventory of every distinct movement of which the body is capable? Until this has been obtained I do not see how we can make any progress in the dynamical part of our business.’ Mr Querulous ridiculed this proposal. ‘ How could you,’ he said, ‘ make any geometrical theory of the mobility of a body without knowing all about the constraints 1 And yet you are attempting to do so with perfectly general con- straints of which you know nothing. It must be all waste of time, for though I have read many books on mechanics, I never saw anything like it.’ Here the gentle voice of Mr Anharmonic was heard. ‘Let us try, let us simply experiment on the mobility of the body, and let us faithfully record what we find.’ In justification of this advice Mr Anharmonic made a remark which was new to most members of the committee : he asserted that, though the con- straints may be of endless variety and complexity, there can be only a very limited variety in the types of possible mobility. It was therefore resolved to make a series of experiments with the simple object of seeing how the body could be moved. Mr Cartesian, having a repu- tation for such work, was requested to undertake the inquiry and to report to the committee. Cartesian commenced operations in accordance with the well-known traditions of his craft. He erected a cumbrous apparatus which he called his three b. 32