April 20, 1883.] 



SCIENCE. 



299 



TBE SOLAR ECLIPSE OF MAY 6. 



The members of the expedition for observ- 

 ing the total solar eclipse of May 6, who left 

 New York on March 2, arrived in Callao, Peru, 

 on March 20. At that port the^- were received 

 by the U.S. A-essel Hartford, and sailed on the 

 22d for Caroline Island, expecting to make the 

 journey . in about twenty-five days. Ample 

 time is thus secured for the preliminary work 

 for the contemplated observations. 



It is not known j-et whether the party will 

 establish themselves upon Caroline or Flint 

 Island. Preference is given to the former, on 

 account of its larger size, and it will be chosen 

 unless it is found that the French astronomers 

 have alread3- located there, in which case the 

 Americans will select Flint Island, that both 

 points may be occupied. The L'Eclaireur, 

 the man-of-war which is to convey the French 

 astronomers from Panama, was not in that port 

 when the Americans passed through tliere. 



The two English members of the part^^ 

 Messrs. H. A. Lawrance and C. Ray Woods, 

 joined the expedition at Panama. Thej^ are 

 sent out bj' the Eoj-al society- and the Com- 

 mittee of solar physics, of which Messrs. 

 Locltyer, Stewart, and Stokes are the leading 

 members, and made important observations of 

 the eclipse of last Ma}^ These gentlemen 

 come from South Kensington, and have been en- 

 gaged in spectroscopic work with Mr. Lockyer. 



The plans of the party show that spectro- 

 scopic observations will be the principal work 

 attempted. An outline of these plans will be 

 of interest. 



A spectroscope with a large prism, attached 

 to a 6J-inch telescope, will be used by Dr. Has- 

 tings for studying the corona, especially the 

 outer corona. During partial phase the chro- 

 mosphere will be examined, a grating being- 

 substituted for the prism. Mr. Rockwell will 

 observe with a grating spectroscope attached 

 to a 433g-inch telescope, and will note the rela- 

 tive lengths of lines reversed just before total- 

 it}- within a small region of the spectrum. 

 Probably just after this, the grating will be 

 exchanged for a single 60° prism, and an ex- 

 amination made of the limits to which the line 

 1474 K can be traced. A prismatic spectro- 

 scope, which consists of a large 30° pirism 

 placed before the objective of a 2|-inch tele- 

 scope, will be used by Mr. Upton for observ- 

 ing the relative heights and brightness of the 

 hydrogen group, and of other portions of the 

 spectrum. Mr. Brown will use an integrating 

 spectroscope for observing the lines which ap- 

 pear during totality, and the changes which 

 they undergo. 



Mr. Lawrance has planned an equatorial 

 stand upon which is mounted a 6-inch objec- 

 tive, having at its focus a grating spectroscope 

 with cameras on each side, for photographing 

 the spectra of the first and second orders. 

 On the same stand is a 6-inch photographic 

 lens, in the focus of which is a spectroscope of 

 low dispersion, armed with a camera. These 

 three cameras will be used to photograph the 

 flash just before and after totality, in order 

 to confirm, if possible, bj- photography, Mr. 

 Lockj-er's ej'e-observations of last year. He 

 observed the short, bright, chromospheric lines 

 ten minutes before totalit3^ began, and, just 

 before totality, the lines which are usually 

 thickened in sunspots, extending as faint lines 

 to a much greater elevation than those of the 

 protuberances. Mr. Woods will employ a sid- 

 erostat to throw a beam of light upon four in- 

 struments, — integrating, analyzing, and pris- 

 matic spectroscopes, and a Rowland grating. 

 The photographic plate of the integrating spec- 

 troscope is verj' long, and will be driven hy 

 clock-work,, in order that, as the portion of 

 the plate illuminated at anj- given instant is 

 small, the integrated effects that have hitherto 

 been photographed maj' be differentiated if 

 possible. The grating is provided with came- 

 ras on each side, — one to photograph the F 

 region ; the other, that more refrangible than 

 H. The prismatic camera was used with great 

 success in Egypt last year. It integrates the 

 light from all parts of the corona ; and it is 

 hoped that all the rays, from the violet to the 

 ultra-red, will be photographed. The analyz- 

 ing spectroscope was also used with good re- 

 sult in Egypt. The plates will be ' red-end ' 

 ones, in order to take in all the rays of the 

 spectrum. 



In addition to the spectroscopic work, other 

 important observations are planned. Professor 

 Holden will search for intra-Mercurial planets 

 with a 6-inch telescope, and Mr. Preston will 

 use a Savart polariscope attached to a 4-inch 

 or a 2-J-inch telescope. Two photoheliographs 

 will be used for photographing the inner and 

 outer details of the corona, under the manage- 

 ment of Mr. Lawrance. Observations of solar 

 radiation, of meteorological phenomena, and 

 of the times of contact, will also be made. 



After the eclipse, the partj' is to be conveyed 

 to Honolulu by the Hartford, from which point 

 thej' will reach San Francisco by the Pacific 

 mail line of steamers. Should there be no 

 delay, intelligence of the results of the expedi- 

 tion maj' be expected by the middle of June. 



W. U. 



CaUao, Peru, March 22, 1S83. 



