Palæontologists might perhaps he excused if they regarded with a certain degree of envy the student of recent organisms, who in addition to other facilities, has at his command that powerful method of research, investigation by means of serial sections. In the case of many important fossils not a half, frequently not a tenth, of the information they could afford, if accessible to this method, has at present been extracted from them. This is the more to be regretted since it is to these ancient forms of life that we must turn for the surest guidance in phylogeny. Serial sections, such as are provided by thin transparent slices are never likely to be very generally employed by the Palæontologist, since they cannot by any known process be obtained at closer intervals than one millimetre or more. Thus it is only when the size of the fossil is so great as to render this interval negligible, that serial thin slices can serve their real purpose. Fortunately the same objection does not apply to opaque sections, such as may he obtained by grinding away the substance of an object; these can be prepared at any desired degree of proximity. Consequently whenever the substance of a fossil, viewed by reflected light, offers a sufficient optical contrast to the enclosing matrix, the method of serial sections may he applied to it. In this matter the Palæontologist has, therefore, no cause for envy; a means for obtaining a deeper insight into the objects of* his study lies ready to hand. The only difficulties are the practical; the object to be studied after having been ground through a known interval, must be removed from the grinding apparatus for examination, and its form recorded by drawing or photography; on replacing it in the apparatus to be ground through a second interval, it must be attached in such a manner that its polished face is returned to precisely the same plane that it occupied before removal. While attempting to devise a machine to accomplish this, I applied for assistance to my friend and colleague Mr. Jervis-Smith, Reader of Mechanics in the University, who at once interested himself in the matter in the kindest way, and solved the problem by designing the apparatus which is represented in figs. 1 and 2, and described by Mr. Jervis-Smith as follows:—“Two planed pillars MM, fig. 1, forming parts of one casting, are supported on a base B. The pillars carry a transverse slide and carriage moving on it, driven by a screw and handle; the transverse slide may be adjusted to any required height from the grinding disc D, by means of screws attached to its back. A plate or chuck E carries the specimen; this plate is attached to a vertical rod, which can be raised or lowered by means of a micrometer screw F, the end of the screw acting as a stop, when the desired amount of the specimen has been removed by the grinding disc D. The wash from the disc is caught in a circular trough A, to which a tube is attached to take away the liquid used in grinding. “The disc D (the diameter of which is 4 inches) is rotated by means of a cord passing partly round the wheels K, H, and entirely round the wheel G. By means of this arrangement of the pulley-wheels the tension of the driving band or cord is maintained between the wheels K and H without the axle of the central wheel being subjected to injurious pressure. The grinding disc is of thick plate-glass, carried on a gun-metal disc attached to the axle of the central wheel. In the process of grinding the disc D is fed with water containing the finest emery flour in suspension. The axle of the wheel K, which is rotated by the handle O, is placed at a small angle with respect to the axle of the wheel H; this prevents the driving cord from rubbing against itself. The slack of the driving cord is taken up by means of the screw N.”
Characterisations in Britain of Isaac Newton’s Approach to Physical Inquiry in the Principia between 1687 and 1713
