Page:Proceedings of the Royal Society of London Vol 69.djvu/231

Rh Largest rainfalls recorded were :

May 8 1-19 inches in 40 minutes.

22 1-72 2 hours.

5. General Programme of the Observations. The operations during the eclipse were to include

1. Taking a series of photographs of the corona with the Dallmeyer

telephotographic combination, in continuation of the series obtained in many recent eclipses, under the direction of the Joint Permanent Eclipse Committee.

2. Taking a series of photographs of the corona with the Savart

camera, used at Algiers in 1900, for a study of the polarisation of the corona.

3. Taking a series of photographs of polarised images of the corona

with the double-image camera, devised and used by Professor H. H. Turner in recent eclipses.

Nos. 1, 2, and 3 were to be done with the "double-tube" camera, which had been used in many eclipses. Professor Turner had very kindly lent me the apparatus for No. 3, but I had most reluctantly to give up the attempt to adjust it ; the weather in the week before the eclipse was unpropitious, and I had to concentrate effort on completing adjustment of instru- ments already set up.

4. Taking a series of photographs of the spectrum of the chromo-

sphere and " flash " at the beginning and end of totality, with a 4-prism spectroscope with slit, for accurate determination of wave-lengths.

5. Taking a photograph of the spectrum of the corona with the

4-prism spectroscope, two slits being used, to get material for the determination of the relative motion of the eastern and western parts of the corona (rotation of the corona).

6. Taking photographs of the " flash " and corona, with a powerful

objective-grating camera, using very high dispersion.

7. Making visual observations of the structure of the green corona

ring, as viewed through another objective grating camera.

8. Taking photographs of the spectrum of the flash and corona with

a quartz spectrograph giving small dispersion.

9. Making visual observations of the atmospheric polarisation with

a view to detecting a change in the plane of polarisation during totality, and for the purpose of getting the information neces- sary for adjusting the Savart camera used in No. 2 during the eclipse.