27 



The instrument consists of a stand supporting a flat triangular 

 box, the corners of which are cut off and occupied by various 

 apertures. One of these is a round hole for the eye of the 

 observer, the other a similar hole for the observed eye ; the 

 third consists of two small separated holes each covered by a 

 small prism. In addition to these a small square aperture is 

 provided in the flat side of the box opposite the observed eye. 

 A candle is placed opposite the two prisms, when the observer 

 sees its reflection from the surfaces of the lens of the observed 

 eye. This is first accommodated for distant objects, and after- 

 wards for a pin placed in the hole immediately opposite ; the 

 changes in the dimensions and positions of the reflected images 

 of the candle flame give the means of determining the altera- 

 tions in the curvature of the lens. 



B. ANTHROPOMETRIC APPARATUS. 



107. Craniometer, an instrument for taking measure- 

 ments of the human cranium. 



Lent by the late George Busk, F.R.S. 1876. 



The instrument is constructed on the principle of the common 

 shoemaker's gauge, and consists of a straight stem about 

 12 inches long, having an arm jointed to it at one end, which 

 can be erected so as to stand at a right angle, and a second arm 

 which can be slid up and down the stem, and is also capable 

 of being erected to a right angle, so as to stand exactly parallel 

 with the former. The stem and arms are graduated on one side 

 in inches and tenths, and on the other in centimetres and 

 millimetres. The graduation of the stem begins at the fixed 

 arm, and that on the arms at the stem. In order to render 

 the instrument capable of taking radial measurements, a conical 

 peg can be slipped upon each of the arms, the points of which 

 are inserted into the external auditory foramina. The radial 

 distance from the centre of the foramen can be thus measured 

 to any point on the periphery of the skull in the mesial plane, 

 the distance being read off on the short arms. 



108. Craniometer designed by Dr. F. W. Spengel. 

 E. 238. 1877. Made by A. Wichmann, Hamburg. 



This apparatus consists of a flat brass table with wooden 

 legs large enough to hold the skull to be examined, and certain 

 movable pieces on each side of it. In the middle of each end 

 is an upright piece which can be moved to and from the centre 

 of the table by means of a fine screw, the distance from the 

 centre being read off on a graduated scale. The skull to be 

 measured is placed vertex downwards upon the table and carefully 

 levelled by small thumbscrews projecting upwards through the 



