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II. The Kinematics of Machines. 
By T. A. Hearson, M.Inst.C.E., Professor of Mechanism and Hydraulic Engineering, 
Royal Indian Engineering College, Coopers Hill. 
Communicated by Professor Cotterill, F.R S. 
Received March 19, 1895,—Read May 30, 1895,—Revised October 31, 1895. 
Whatever machine he examined, it will be found to consist of a number of pieces, 
each of which is connected with one or more other pieces, in such a way as to be 
capable of some kind of motion relatively to those pieces. 
The nature of the relative motion will depend largely on the form of the surfaces of 
mutual contact, but also on other influences. In some cases it will be of a simple 
character, in others, more complex. 
It is proposed to refer to these as the elementary mechanical motions, and to regard 
a machine as an embodiment of a number of such motions which, together, provide 
that particular kind of, more or less complicated, movement which is required to serve 
the purpose of the machine. 
The principal object of this paper is to indicate certain geometrical laws which 
govern the association of these elementary mechanical motions in the composition of 
machines, and it will be shown that in the examination of the influence of these laws 
one is led to a systematic classification of all machines, and to the enumeration of an 
exhaustive list of some, if not all, classes of simple machines. 
Further, the idea that a machine is an embodiment of a combination of elementary 
motions (of which it will be found that the number of kinds is comparatively limited), 
enables one, by adopting a suggestive symbol for each, to indicate the composition of 
every machine movement by means of a simple formula. 
If the machine consists of only two separately moving pieces then only one 
elementary motion will be involved in the construction. 
If there are three pieces, V, X, and Z, for example, Y and X may be joined to and 
in contact with Z, but not connected with one another. In this case the motion of 
Y relatively to Z will be quite independent of the motion of X, and the apparatus 
should be regarded as a compound mechanism having one link, Z, common to two 
simple mechanisms. 
If Y and X are connected together, then, under some circumstances, relative 
motion of the three pieces will be possible, and there will be three motions included in 
the mechanism, which will be related to one another. 
27.2.96= 
