278 Salisbury . — Methods of Palaeobotanical Reconstruction . 
For the purpose of this apparatus the model is built up on a circular 
disc of wood A, of the same size as a rotating platform, B, in the instrument 
itself, upon which it rests. The disc bearing the model is removable and 
engages with the platform by means of three pins projecting from this 
latter, which are arranged in an asymmetrical manner so that the model, 
when removed, can only be replaced in the original position. The lower 
disc is attached by its axis to the rising and falling platform C, which moves 
along four upright metal guides, d', d '\ d '", t >"'\ fixed below into a base- 
board, and above carrying the rectangular framework E, which is further 
supported by uprights. 
The effective length of the guides determines the extreme height of the 
models which can be cut. In practice a twelve-inch model has usually been 
found to give sufficient magnification for all purposes. 
When the platform is at the highest limit the upper surface must be 
just above that of the rectangular frame ; the internal width of this latter is 
slightly greater than that of the platform, whilst its length is more than 
double and so placed that the model is at one end. 
A second frame, F, open at one extremity is hinged by the two free 
ends on to the upper sides of sliding runners which engage with grooves on 
the inner side of the horizontal frame. The hinges permit the former to be 
placed at any angle, whilst supports from its upper end, G r , g", enable it to 
be clamped in the desired position. 
The model is cut by a taut wire drawn down the surface of the hinged 
frame, and scales appropriately placed give the necessary data as to the 
direction of the section, viz. the angle of the cutting plane ; the position 
which the base of the frame F occupies along the horizontal grooves ; the 
height of the rising platform ; and the angle of the rotating platform. 
It will be seen that such a mechanism enables one to cut the model in 
every possible direction, whilst the rising and falling platform can also, 
by clamping it at equal or unequal distances, be used for reproducing serial 
sections. 
When utilizing the above for the elucidation by trial of the direction 
of a section which we have been unable to plot, the plane can be approxi- 
mately arrived at by constructing a wire frame of the same shape as the 
outline of the section and placing this on the uncut model. In this way 
numerous trial sections can be avoided and thus much time spent in 
modelling is saved. 
Whilst this instrument was constructed for the purpose of palaeobotanical 
research the use of some such check on one’s observations might be of 
great advantage in other branches. Lawson has pointed out that the 
lateral position of the synaptic knot is probably often exaggerated owing to 
the obliquity of section . 1 And it may be that the effect of this on the form 
1 Trans. Roy. Soc., Edinburgh, 1911. 
