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In this paper the author gave numerical results derived 
from measurement of the astigmatism of an eye, extending over 
a considerable period of years, which shewed that during this 
time there had been a change in the astigmatism. 
Mr Paine observed that he had found from his experience 
as an optician that about 1 in 100 suffered perceptibly from 
astigmatism, and described the mode of correcting it by glasses. 
He said that when astigmatism existed in the crystalline lens 
it was difficult to remedy it; but not so when it was in the 
cornea. It was generally supposed that the astigmatism did 
not alter with age, so that the Astronomer Royal’s observations 
were of much interest, as they shewed a change. 
Professors Miller and Maxwell, Mr Trotter and Dr Latham 
also made some brief remarks on the subject of the paper. 
(2) The comparison of measures & traits with measures 
& bouts. By Prof. Miuuzr, F.R.S. 
A standard of length in which the measure is defined by the 
distance between certain points in the surfaces by which the 
two ends of a material bar are respectively bounded is called a 
measure @ bouts. A standard in which the measure is defined 
by the distance between two fine lines traced at right angles to 
the axis of the bar is called a measure @ traits. The methods 
of comparing with one another two measures of the same kind 
are well known and need not be alluded to here. But the 
comparison of a measure @ traits with a measure @ bouts cannot 
be effected so readily. The Astronomer Royal, on being con- 
sulted respecting the best method of making such a comparison, 
recommended the following process. Two copies, AB, DH, of 
the original standard @ bouts are constructed with cylindrical 
cavities at their middle points reaching down to the points 
C, F in the axes of the bars, where lines are traced at right 
