Page:Proceedings of the Royal Society of London Vol 69.djvu/282

266 This negative is fainter then any of the others, but shows well the detail and prominence in the south-west region of the corona.

4. The Waters Camera.

This is a Dallmeyer portrait combination of 2 inches aperture and 8 feet equivalent focus, a Dallmeyer telephoto lens being used as a negative enlarger. The photographs were taken on half plates. The enlargement is rather too great for detail of any importance to be shown, and there is therefore no need to describe them in detail. Exposures of about a quarter of a second were given in all cases.

No. 1. Exposed at second contact. Plate, Imperial Special Rapid. No. 2. Exposed at 40 seconds. Plate, Imperial Special Kapid. No. 3. Exposed at 80 seconds. Plate. Imperial Flashlight. No. 4. Exposed at 120 seconds. Plate, Imperial Flashlight. No. 5. Exposed at 160 seconds. Plate, Imperial Flashlight. No. 6. Exposed at 200 seconds. Plate, Imperial Special Kapid.

5. The Pinhole Camera.

This was a camera with pinhole aperture of ^V of an inch, and the plate was placed at a distance of 30 inches. The plate was exposed immediately before second contact, and closed immediately after third. A small arc of sunlight is thus seen both on the east and west limbs of the Moon. A coronal ring, about 4 minutes in greatest height, is seen connecting these arcs. The little photograph has of course no scientific value, but as being the only instance of a photo- graph of the corona taken with a pinhole, it may rank as a curiosity. The ratio of aperture to focal length was as 1 to 960, and the exposure given to the plate would correspond to one of y^th of a second, as given with the Newbegin. The plate used was an Imperial Special Eapid.

6. Photographs of the Landscape.

At my request M. Alexander Rambert, a professional photographer of Mauritius, took a series of photographs of the landscape during the coming on and passing off of the shadow. The same exposure was given in every instance, the plates were all from the same batch, and they were developed at one and the same time, in the same bath and for the 'same length of time. The exposures were made at regular intervals of 5 minutes, the first being taken 27 minutes before mid- totality, the last 27| minutes after. A comparison of the plates taken before totality with those taken at corresponding times after, shows a slight but appreciable increase in density in the later plates as com- pared with the earlier, but perhaps not more than would be accounted for by the increase in altitude of the Sun.