114 
Proceedings of the Royal Irish Academy. 
a telescope of 2 inches aperture, besides a modified Savart's polari- 
Bcope of great sensibility, but having a small field, not telescopic ; 
Mr. Clifford had a biqnartz also, I believe, on a telescope ; Mr. Ran- 
yardy who was stationed at Yillasmonda, seven miles west of Agosta, 
at an elevation of about 600 feet above the sea, had a 2-75-inch or 
3-inch achromatic, fitted with a biquartz, the finder having a quartz 
plate as a cap. The Author had Mr. Buckingham's equatorial achro- 
matic, with a 5 -inch object glass, fitted with a Herschel-Browning 
direct vision spectroscope with two prisms, whose dispersion was equal 
to 1^ times that of a flint glass prism of 60°. This instrument showed 
the line D double, and also the close pair of the group h. There was 
no driving clock. 
Preliminary experiments were made on the morning of the 22nd, to 
test the capability of the instrument for detecting protuberances, the 
slit being set to such a width as would permit distinct vision of some 
60 Prauenhofer lines — the intention being to get as much light as pos- 
sible, consistently with allowing the detection of dark lines in the 
corona spectrum — supposing that they co-existed with sufficient in- 
trinsic brilliancy. The protuberances were readily caught with a 
tangential slit, the forms even of some of them being rendered visible 
by a rapid vibration imparted to the instrument. The principal pro- 
tuberances were mapped for my own use and that of others who 
wished to know their position. It was of course, desirable, as far as 
possible to avoid them, and thus to get the pure spectrum of the 
corona. It was found that the E. and W. points of the sun's limb were 
very free from protuberances. Accordingly the following plan of 
operations during totality was determined upon. 
The slit was set north and south, i. e. in a circle of declination, 
and the four points of the sun's disc, E., W., JST., and S., were fixed 
upon to be examined in succession with the slit, the direction of 
which, referred to any great circle, was to be retained constant during 
the observations. My assistant at the finder. Sergeant Ring, E. E., 
was instructed at the moment of commencement of totality to point 
the instrument on the corona immediately outside the E. point of the 
moon's limb. When that region had been observed, he was to point 
similarly at a place immediately exterior to the W. limb, then we 
were to proceed to the north, and end our pre-determined work at 
the south point of the limb. 
By this method of working, we hoped to obtain with the slit tan- 
gential at E. and W. limbs, the spectrum of the lower regions of the 
corona. Then, the radial slit at IS", and S. would enable me to compare 
the spectra of the upper and lower regions, which would be visible 
in the same field, the visible length of the slit being nearly 8' of arc. 
After this, if there was time still remaining, we hoped to secure 
the spectrum of any other part which should seem brightest to the 
Sergeant at the finder. 
It should here be remarked, that the finder was non-inverting, 
being an ordinary pocket spy-glass, kindly lent by the Colonel in 
