146 Proceedings of Royal Society of Edinburgh. [sess. 1 
existing records. Take, for example, those made by Captain Jacob in 
Madras in 1856-57-58 compared with those of Captain Tnpman 
in the Mediterranean in 1869-71. 
The former * found that the axis of the light was inclined but 1 
slightly to the ecliptic, and that the extreme positions of the vertex 
of the western cone were lat. 2° S. and lat. 6° 17., while the latter 
states f that the inclination to the ecliptic was often as much as 20°, 
and that an error of 3° or 4° in his observations is inadmissible. 
It is extremely difficult to fix the position of the light by any of 
the ordinary methods, but I have hopes of getting a very fair 
estimate of the inclination of the axis by using a form of clinometer. 
This consists of a stand with levelling screws carrying a long wooden 
arm movable in a vertical plane about an axis at one end, and 
provided with an arrangement for clamping it at any required 
angle. The angle is measured by means of a plumb line suspended 
from the upper end. I find it possible to place this arm parallel to 
the axis of the light with considerable accuracy. At the same time 
it seems probable, as remarked by Searle, that no really satisfactory 
determination of the position of the light will be obtained except 
by a careful photometric survey. A method of making such a 
survey has, however, still to be devised, and to be satisfactory it 
would have to be preceded by a photometric survey of the region 
in which the light falls. 
On the Structure and Contraction of Striped Muscular 
Fibre of the Crab and Lobster. By Professor William 
Rutherford, M.D., F.R.S. 
(Read February 28, 1890.) 
{Abstract.) 
The author gave an account of the microscopical appearances of 
striped muscle of the crab and lobster. The muscle of the crab and 
lobster is suitable for investigation because of the comparatively large j 
size of the structural elements, and the readiness with which the 
sarcous matter can be fixed and otherwise prepared in different con- 
* Memoirs R. A. S., vol. xxviii. p. 119. 
t R. A. S. Monthly Notices, xxxi. p. 74. 
