358 
Proceedings of Royal Society of Edinburgh. [july 4, 
On looking at the cell again, about eight months later, the copper 
wire was found corroded through, and contact broken. In order to 
avoid this accident, it is well to use copper rod not less than one- 
eighth of an inch thick, as copper is somewhat soluble in solution of 
sulphate of copper (see Gray, Phil. Mag., 1886, p. 389). 
The corks used to support the copper and zinc rods should he 
carefully paraffined, and every precaution taken to prevent evapora- 
tion of the solutions. 
The observation in the above table, dated May 31, was taken 
rather hurriedly, and Professor Ayrton considers it untrustworthy. 
Omitting this result, it is seen that the experimental cell has a very 
constant E.M.F., and that the change, after about five months, was 
very small. 
7. On Glories. By Professor Tait. 
(Abstract.) 
When Mr Omond was appointed to the Ben-Hevis Observatory 
I requested him to take every opportunity of observing what are 
called Glories — specially noting, when possible, their angular 
diameters and the order of their colours, so that it might he 
possible to decide upon the exact mode in which they are produced. 
Young, while attributing to their true cause the spurious (or 
supernumerary) rainbows, proceeds to say: — “ The circles, some- 
times seen encompassing the observer’s shadow in a mist, are 
perhaps more nearly related to the common colours of thin plates 
as seen by reflection.” — \_Lectures, II. p. 645]. 
How from Mr Omond’s observations it appears that the mists to 
which the glories are due produce coronse of, say, 2° or 3° radius ; — 
from which it follows that the diameter of the particles is some- 
where of the order yqW i nc b. It is thence shown that, were 
Young’s explanation correct, the radii of the rings would vary with 
great rapidity in passing from one kind of homogeneous light to 
another. This is altogether irreconcilable with Mr Omond’s obser- 
vations. 
That the glories are not of the nature of spurious rainbows is 
shown very simply by the fact that they are more intense as their 
radii are smaller. 
