184 
Proceedings of the Royal Society 
Ushas, Sarasvati, &c. &c. The writer then sums up the instances of 
well established coincidence between the Indian and the classical 
deities, which he considers to be few in number ; and concludes by 
noticing how the most prominent gods of the Eigveda lost much of 
their importance in the later mythology of India, while two of the 
deities who hold only a subordinate rank in the Yeda — viz. Vishnu 
and Rudra — were afterwards’ exalted to the highest position. 
2. On the Diffraction Bands produced by Double Striated 
Surfaces. By Sir David Brewster, K.H., F.E.S. 
Having observed a series of serrated fringes in examining the 
colours produced by the fibres of the crystalline lens of fishes, the 
author was led to imitate them by the combination of grooves 
upon glass and steel surfaces, or of grooves taken from these sur- 
faces upon isinglass or gums. 
The interference bands thus produced were serrated or rectilineal, 
sometimes parallel and sometimes at right angles to the direction 
of the grooves, and varying in their magnitude and character ac- 
cording as they were exhibited on the colourless image, or on the 
diffracted spectra, or as they were produced at different angles of 
incidence, or at different distances of the grooved surfaces, or by 
different numbers of reflexion, or by different numbers and combi- 
nations of refracting and reflecting surfaces. 
The grooves on glass employed by the author were executed by 
the late Mr G-eorge Dollond, and those on steel, varying from 315 
to 10,000 in an inch, by the late Sir John Barton. 
3. An Essay on the Theory of Ooinmensurables. By Edward 
Sang, Esq. 
The subject of this essay may be described as an application of 
the Theory of Number to G-eometry, its principal or characteristic 
problem being to determine under what conditions the sides or sur- 
faces of figures may be represented by integer numbers. 
Like all other inquiries into the properties of integers, it is rather 
speculative than practical, and yet, perhaps on that very account, 
is more apt to engross the attention of its cultivators than almost 
any other department of pure mathematics. It seems, indeed, to 
be of very little moment whether we can demonstrate that the sum 
