248 A. E. Dolbear on a Method of 
it appears to present no essential difference except that of size, 
The first phalanx, however, shows in its proximal end several 
differences which are clearly of specific importance. The outer 
articular surface in the present specimen is proportionally much 
narrower, and has its posterior margin more exten TOXI 
mally. ‘There is, moreover, no indication, on the inner side of 
the bone, of the large obtuse tubercle which is a prominent fea- 
appeared from the present specimen, leaving an elongated oval 
h 
depression, with a we th of the above 
bones are somewhat distorted by pressure. 
Measurements. 
Transverse diameter of win tacarpal, at distal end,...26° ™. 
Proximal extent of outer condyle, on palmar side, ------ 22°6 
oximal extent of inner condyle,__.._...__----------- 0° 
Transverse diameter of shaft at junction with condyles, .-21 
Antero-posterior diameter of proximal end of first phalanx,38° 
Greatest transverse diameter, _.......... _.----------- 12° 
The specimens of this species at present known do not afford 
perfectly reliable data for estimating the size of the animal, but 
the wings, when fully expanded, were probably from twelve to 
fifteen feet in extent. The fossils here described were found 
by the writer, in July last, in the gray cretaceous shale, on the 
south side of the Smoky River, in Kansas. 
Yale College, New Haven, Conn., Feb. 26th, 1872. 
Art. XXX.—On a new method of measuring the Velocity of 
Rotation ; by Prof. A. E. DoLBEAR. 
WHILE experimenting with the gyroscope, I have often 
wished to know its velocity, but knew of no way to peor 
it when it was set in motion in the usual way with a string: 
have lately found a simple and exact way of doing this, ee 
description of the plan may be of interest to others, as it can 
used to measure the velocity of wheels of every size, and every 
possible speed, without inconvenience and without expense. ‘ 
If a short piece of wire be soldered to the end of one brane 
of a common tuning fork, one end of the wire projecting * 
little on one side, and the fork made to vibrate at the same time 
is has been used to determine linear velocity ; but it can so 
a 
be applied to rotary with great precision. I have a large fork 
