The following investigations were commenced about nine years ago, and some of the results were laid before the Physiological Subsection of the British Association Meeting at Manchester in 1861. Circumstances, during a series of years, prevented the writer from elaborating so fully as he desired the results of the measurements which he had already made ; but this is the less to be regretted, as in the meantime he has had opportunity of making additional measurements, and the writings of others which have from time to time appeared have given him additional information without interfering with the line of inquiry which he proposed to himself to pursue. That inquiry was commenced in the belief that descriptions of crania expressing, however precisely, the surface-peculiarities which meet the eye, were not sufficient to determine the real nature of the differences existing between the crania of different nations or individuals ; that it was necessary to consider the arch and the base of the skull in their connexion one with the other, and to measure the relations of parts by means of distances and angles more systematically than had been done ; and that if this were done it would appear that there were far more important variations in the antero-posterior direction in skulls than were suspected, or than existed in their breadth. The various forms of forehead, vertex, and occiput are noted by anatomists without sufficient knowledge how these local appearances are related to the structure of the cranium as a whole. Even such generally used words as dolichocephalous, brachycephalous, orthognathous, and prognathous, though efforts have been made to render them perfectly explicit, refer to varieties of form which have not been properly understood. Mode of
measurement
. —It may be frankly admitted that probably the system of “geometrical drawing” recommended and described by Lucae * would have been preferable in some respects to the mode of craniometry employed by the writer, but most of the measurements were made before Lucae’s method was published. Also it may be admitted that vertical sections, which afford the most accurate of all bases for profile views, might have been used to a greater extent than they were; but there was a difficulty in asking that a number of skulls in Museums should be bisected for examination by a private individual. Still some bisections have been obtained, sufficient to illustrate the substantial accuracy of the system in most instances followed; and while mentioning this, it is right to say how much indebted the writer has been to the late Professor Goodsir and Professor Allman of Edinburgh, and to Professor Allen Thomson, for their kindness in placing specimens at his disposal. The craniometer which the writer has employed is not without its advantages, being an instrument fitted to determine the exact relation of any point in space to a given starting-point. The skull is suspended in a horizontal frame by means of two pointed screws, one on each side, which work in fixed supports; and by other screws moving on slides it may be set with any two points on a level. A vertical bar, which can be slipped up and down, slides along the side of the frame, and bears a sliding horizontal bar directed inwards, to which a needle may be attached at right angles if necessary, in either a vertical or longitudinal direction. The frame, the bars, and the needle are all marked off in inches and tenths, and by this means the vertical and horizontal distance of any point on the skull from the place of suspension is easily determined and marked on paper, so that by a series of such points a diagram may be constructed. With the assistance of a sheet of ruled paper such a diagram may be constructed in a few minutes from a series of figures not occupying more than a couple of lines. It is convenient to register the number indicating the vertical position of a point with that indicating the horizontal position placed immediately below it, like the denominator of a vulgar ^fraction; while backward and downward directions may be respectively distinguished from forward and upward directions by placing — before the figure. Thus the following formula is sufficient for the construction of a diagram of the Irish skull 54:— -.4/.05 -.7/-1.35 .1/1.05 -.65/1.9 -1.2/3.5 -6/3.65 -.3/-3. .75/-3.65 1.9/-3.65 4.4/-2.3 5./.55 3.85/3.05 1.8/3.65 1.3/3.55 1.1/1.5 If to this formula there be added the breadth at as many points as may be desired, and the positions of those points, the utmost completeness may be given to it. By this system of notation the outline of the profile of every skull in every Museum might be recorded with the greatest accuracy, either from measurements taken with the craniometer described, or from geometrical drawings, or tracings of vertical sections.
Cloud geometry from oxygen-A band observations through an aircraft side window
