6 REPORT—1858. 
line cutting the arcs in two points, from which were projected upon the tines in the 
triangle other points, these last being the points for the desired hyperbola. See figure, 
In the second it was shown how to apply this problem in forming the model by 
which to work the shafts of columns with hyperbolical entasis, the subject being 
illustrated by exhibiting the contour of a column of the Parthenon. 
On a mode of constructing Tables of Squares and Cubes. 
By C.M. Witxicu, Actuary, University Life Office. 
Licut, Heart. 
On Heat and on the Indestructibility of Elementary Bodies. 
By Miss Rosina Zornuin. (Communicated by S. W. Ayrton.) 
On the Duration of Luminous Impressions on certain Points of the Retina. 
By Sir Daviv Brewster, KH, F.RS. L.& BE. 
It is well known that the duration of luminous impressions on the retina is one- 
third of a second for white light of ordinary intensity. In the Report of the Belfast 
