50 



KNOWLEDGE. 



[Makch Ir- 1900. 



totality 94 seconds. At Cape de Santa Pola, on the 

 east coast of Spain, near Elclie. the altitude has 

 diminished to 34°. the duration to 79 seconds, and the 

 local time of mid-totality is 4.11 p.m. As in the 

 United States, corresponding particulars may be in- 

 feiTed for any intermediate place from its distance? 

 from these two extreme stations. 



So far as the weather conditions are concerned, th^ 

 prospects iu Portugal are much the least favourable, 

 the stations on the western slops of the Serra 

 D'Estrella generally suffering from the drawback that 

 the aft.ei-noons are cloudy at that time of the year. 

 Broadly speaking, so fai' as at present known, the 

 weather in Spain would seem to be likely to be all that 

 can be desired, whether on the central table-laud or 

 down near the coast neai- the department of Alicante. 



When we cross to Algeria we find the sun's altitud.3 

 very nearly the same as at New Orleans ; 29° 

 instead of 30°, and the duration is only 71 seconds. 

 The mid-eclipse takes place here at 4.31 p.m , loca' 

 time. It is not likely that any observers from England 

 will go further east. 



The weather probabilities not greatly favoiu-ing Portu- 

 gal, and especially the coast, probably but few parties 

 will try that counti-y. It ought certainly not to b^ 

 entirely neglected, for the experience of fonner eclipses 

 has shown again and again how completely the mosi 

 careful cloud forecasts will sometimes be falsified by 

 the event. Two railways run north from Lisbon the 

 one along the coast through Coimbra will give accesi 

 to Ovar on the coast, or to Viseu inland ; the other, 

 striking inland towards Salamanca, will lead to 

 Sabugal. These three places seem to be the mosi 

 accessible on the central line in Portugal. 



In Spain the principal places on or near the central 

 line and accessible by rail are Plasencia, Navalmcral, 

 and Oropesa. All three can be reached by rail frorn^ 

 Lisbon or Madrid. Talavera de la Eeina is the pi-in- 

 cipal town upon this line, but the duration here is not 

 quite 50 seconds, Talavera, though within the shadow, 

 being a good deal north of the central line. Further 

 east, Toledo just escapes the total phase, being a few 

 miles north of the northern limit of the shadow, and 

 from this point onwards till we reach the coast no 

 tcwns of great importance are intersected by the line of 

 central eclipse, though two railway lines, — on the more 

 easterly of which is Alcazar, a considerable railwav 

 junction, 15 miles north of the central line, — run south 

 from Madrid and meet at Ciudad Real after crossing 

 the shadow track. But by far the most accessible 

 places, especially for those with any considerable equip- 

 ment, are Alicante and Algiers. Neither are quite on 

 the central line, but the duration at Alicante will bs 

 72 seconds and that at Algiers 66, and, so far as it is 

 possible to predict, the probability of a very pure skv 

 is great for the neighbourhood of both cities. 



So far as at present arranged the distribution of the 

 English ofiicial parties will be somewhat as follows: — 



The Astronomer-Royal and Mr. Dyson, from the 

 Roj^al Observatory. Greenwich, will probably occupy a 

 s.ation in Portugal near Ova'-. Sir Ncrman Lockyer, 

 who will be accompanied by Mr. A Fowler and per- 

 haps other assistants froji the Sou^ 'i Kensington Ob- 

 servatoiy, will take his place near Alicante; whilst 

 Algeria has been chosen bv Mr. Evershed, and Prof. 

 Turner and Dr. Common will probably choose the same 

 district. 



The British Astronomical Association are engaging 

 the splendid st<>amer " Tagus," of the Royar Mail 



Steamship Co. s line, to t.ake observers to Alicante and 

 Algiers direct from England, and have arranged to 

 call at Cadiz for the convenience of those who wish to 

 observe the eclipse at Alcazar, and to combine with it 

 a tour in .Southern Spain. A second expedition, under 

 the leadership of the Rev. J. M. Bacon, f.r..\.s., will pro- 

 ceed to the United States, probably taking their 

 station at Newberry, South Carolina. 



The most important items in the programme of ob- 

 servations as yet determined upon appear to be Sir 

 Norman Lockyer's scheme for obtaining the " Flash " 

 spectrum with a very mucli larger solar image than ever 

 attempted before; Mr. Evei-shed's, to prolong the 

 " Flash " by choosing a station near the eage of the 

 shadow; and Dr. Common'^, to imitate Mrs. Maunder's 

 photographs of the coronal sti-eamers with much moro 

 powerful instruments. 



It may be assumed that the numerous methods of 

 observation, photographic or visual, carried out or 

 attempted in joast eclipses, will be again tried next 

 May. Photogi-aphs of the corona will be taken on all 

 scales, from that giving the sun a diameter of 4 inches, 

 such as the Astronomer-Royal obtained in India with 

 the Thompson heliogi-aph of the Royal Observatory, 

 Greenwich, to that which gives the sun a breadth of 

 but a vei-v small fraction of an inch. 



It may be again emphasized here that those photo- 

 graphers whose object-glasses have an effective ratio of 

 aperture to focus not exceeding 1 to 15 or 16, will be 

 well advised to discard any form of equatorial mount 

 or driving clock, with its liability to shake, and in- 

 sidious temptation to overexpose, and rigidly fixing 

 the camera, to give exposures not exceeding one second 

 as a maximum. 



Both before and after totality a series of photo- 

 graphs should be taken of the Partial Phase. Since 

 but one photograph has as yet been ob+ained of the 

 Corona after totality was well over, no definite rule.: 

 can be laid down as to the style of instrument that 

 should be employed. Therefore in this next eclipse all 

 sorts of cameras might be pressed into the sei-vice, and 

 some range of exposiu-e should be given. One thing 

 is certain; 'hat in all cases the development must be 

 canied out with the special object of restraining the 

 high lights and giving r opportunity for the feeble 

 radiations to register. 



Mr. Nevil Maskelyne will kinematograph the corona 

 at his station in America. A most interesting and in- 

 structive use for the kiaematograph in the coming 

 eclipse would be its adaptation to the experiments 

 which Miss Gertnide Bacon carried out in India on 

 the illumination of the landscape during the Partial 

 Phase. In a series of five photographs, taken at equal 

 intervals. Miss Bacon found the curious fact confirmed 

 (hitherto believed to be an optical illusion) that the 

 illumination returned more rapidly after eclipse than 

 it diminished before eclipse. The kinematogi'aph, if 

 used for this pui-pose, would give a more even and con- 

 tinuous series, and if it were possible to use more 

 than one in the same locality, would decide whether 

 the same effect held good when the instrument was 

 pointed in the direction from which the shadow was 

 approaching and towards which it was receding. 



Akin to this observation is that of the general il- 

 lumination of the corona, which may be determined 

 by very simple photographic sensitometcrs. In India 

 this was determined photographically by Mr. E. W. 

 Johnson (using a sensitometer constructed by Mr. 

 Gare) and by the Rev. J. M. Bacon, and visually by 



