MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES/ 169 



briskly over the moistened surface with the thumb nail. Treat the entire figure in this way. If 

 a reverse picture is wanted, which is usually the case when a finished drawing is to be prepared 

 for engraving, ink the scratched line and take the imprint therefrom. 



If it is desired to prove the correctness of a positive picture, wash away the ink from which 

 the imprint has been made, ink the scratched drawing and place it right side up over the positive 

 on the paper. The two should correspond. In no instance where we have made this test have we 

 found the slightest error. 



We have used an ordinary black ink, and have been able to take three good impressions from 

 one drawing. If it were desirable to take a large number of copies, other inks could be found to 

 accomplish the purpose. 



Dr. Paul Topinard tell us* that with Broca's stereograph the five views of the skull may be 

 made in an hour. It takes nearly twice that time to do the same with our contrivance, operating 

 with proper care; but as a partial compensation for this we have a drawing which furnishes many 

 duplicates. 



No special skill or lightness of hand is required with our apparatus; any person possessed of 

 ordinary intelligence and eyesight can use it successfully at the first trial. It is not complicated ; 

 it requires no highly skilled workman to construct it; it may be made by any carpenter and its 

 cost is insignificant. 



Even the periglyph may be made by any handy individual with an ordinary pocket knife. 

 We have two periglyphs, one manufactured of metal by a practical model-maker, the other rudely 

 whittled out of wood by a medical gentleman connected with the Museum; both are perfectly 

 accurate, but the latter is the more easily handled and the favorite instrument. 



Several outlines may, without confusion, be drawn on the same varnished surface. The 

 varnish should be of such a character that when dry it becomes crisp and brittle, breaking up in 

 the course of the stylus not dragging after the instrument and clogging it. Of many mixtures 

 tried that known in the trade as Berry Brothers' (Detroit) hard-oil finish, diluted with one-third 

 turpentine, gave the best results. 



I n making all but six of these tracings we adjusted the skulls on the German horizontal plane, 

 or plane of the Frankfort agreement, partly for the reason that with the sand box we could find 

 this plane more readily than we could find the alveolo-coudylean plane. But for purposes of com- 

 parison we sketched the norma verticnlis parallel with the alveolo-coudylean plane in six speci- 

 mens, the type skull and five which approximated the type. The reduced tracings are shown in 

 plate 51. 



The five views of the type skullt (Pis. 55-59, incl.) were made on the basis of elaborate 

 orthogonal tracings, the shading being added by the artist from nature. They are natural size. 

 It is greatly to be regretted that the nasal bones in the type skull were broken, and that we were 

 obliged to make a plaster restoration. The shape of the nasal aperture is only approximate. 



There were but few skulls in this series in which all the points of the German horizontal plane 

 or any other horizontal plane could be found to coincide with a true horizon, while the sagittal 

 plane was perfectly vertical to such horizon. The variance was most marked at the upper borders 

 of the auditory meatuses. In order to approximate uniformity we always aligned our facial 

 guiding marks, not with the upper margin of the right meatns, but with that of the left, the side 

 on which the norma later alls was taken. 



The views of the lower jaws in plates 52^ 53, and 54 were taken with the same apparatus 

 and by the same method as were those of the skulls, and similarly reduced by the pantograph. 

 Whe.n each was drawn the plate of glass on which the tracing was made was parallel to the plane 

 on which the lower margin of the jaw rested at equilibrium. 



Areas in the drawings marked with parallel straight lines show where there are holes in the 

 skulls, neither bone nor plaster being present. Dotted areas indicate plaster restorations all 

 such repairs, whether deep or superficial, being thus shown. 



"Op. tit., p. 863. t For description see $ 14. 



