THE TOTAL SOLAR ECLIPSE OF APRIL 6, 1875. 
141 
of one part only of the corona, but that it gives us a combined representation of the 
spectrum of every part of the corona and chromosphere, and that careful examination 
of the result enables us to analyse it into its constituents. 
The Spectroscopic Camera. 
The chief drawback of the prismatic camera consists in the difficulty of obtaining 
a scale by means of which the refrangibility of the different rays can be determined. 
In order to complete the preparations as much as possible, it was arranged to 
endeavour to obtain photographs of the spectrum of the prominences by means of a 
telescope and ordinary spectroscope, the slit of which was provided with shutters, so 
that the solar spectrum could be photographed and used as a scale either before or 
after totality. It was hoped that photographic impressions of at least the brightest 
lines of the chromosphere could be obtained and identified by means of the solar 
spectrum. These brightest lines could then have been easily recognised on the plates 
of the prismatic camera, and would have formed a scale for the weaker protuberance 
lines and other phenomena visible on the plates. 
Before discussing in detail the results, we have to give a short account of the 
journey and the preparations. 
II. CHOICE OF STATIONS. 
Three stations were available for the observation of the eclipse. The eastern coast 
of the Malayan Peninsula (Siam), the western coast of the Malayan Peninsula, and 
the Nicobar Islands. As the weather was rather doubtful during the month of April 
at all three stations, it was decided to divide the expedition into three parts. 
Although the journey to Siam was much longer, and much less time was therefore 
left for preparations on the spot, the liberal invitation and offer of help by the King 
of Siam, made it certain that all possible preparations would be made before the arrival 
of the expedition. Circumstances over which the expedition had no control prevented 
them from carrying out the original plan of sending some of the observers to Mergui, 
on the western side of the Malayan Peninsula. There were observers therefore at two 
stations only ; Lem Chulie, in the Malayan Peninsula, and Camorta, in the Nicobar 
Islands. 
III. THE EXPEDITION TO SIAM. 
Journey to the Observatory. — Preparations for the Eclipse. 
The expedition left Southampton on February the 11th, in the Peninsular and 
Oriental Steamship ‘ Surat.’ It consisted of the following gentlemen : — 
