June 8, 1882] 



NA TURE 



129 



some religious conception, we might feel inclined to trace 

 the origin of American cup-cutting to Asia. But if, on 

 the other hand, the cups were designed for a practical 

 purpose, the custom of excavating them may have sprung 

 up in America, as well as elsewhere. 



THE ECLIPSE EXPEDITION 

 '"THE following letter from its Special Correspondent 

 A with the English Eclipse Expedition, appeared in 

 the Daily Nexus of Tuesday : — 



Soling, May 19 



Still at Sohag ! but how different is the place now from 

 what it was when I first sighted it — as it seems, years ago. 

 Then the solitary steamer and the tents of the French 

 party were hardly sufficient to break the shore line as we 

 looked at it, alas for too long a time, from the place of 

 our last ensablement. But now the steamer is lost in a 

 fleet of dahabeeahs, and the line of tents and shelters has 

 been extended for some distance towards the town ; but 

 tents are coming down, the hot sand is being strewed 

 with boxes, and in 24 hours nothing will be left but some 

 brick piers, which the next high tide will make short work 

 with. Yes, something will be left. Sohag will have taken 

 its place in scientific history by the side of many other 

 out-of-the-world places, which seem to be chiefly affected 

 by eclipses, and its memory may still puzzle the dryasdusts 

 of the future. 



As the 17th approached the excitement of almost every- 

 body visibly increased, and as the energy waned the 

 tension waxed. A little wind eddy of fearful violence, 

 which produced a small sand-storm on the land, and 

 almost a waterspout as it tore its way out of sight across 

 the Nile, after hurling down one of the French tents and 

 driving the dahabeeah occupied by the English party 

 from its moorings, was almost a relief ; and a further 

 variety' was introduced into the monotony of heat and 

 work by the arrival of the dahabeeahs and the final visit 

 of the Governor-General to the astronomers and his new 

 visitors, Aly Pacha Cherif (son of Cherif Pacha, Minister 

 of Mohamet Aly) ; Osman Pacha Galeb, Governor-General 

 ofAssiout; Mahmoud Pacha, director of the Cairo Ob- 

 servatory ; Mohamed Bey-el-Kakim, and others being 

 among them. On this occasion the Governor-General 

 Aly Pacha Riza was accompanied by Teidrous Effendi, 

 chief judge, and Mohamet Effendi Kamil, one of the 

 judges of his province, and his aide-de-camp Moustafa 

 Effendi Sirry. The commandant of the garrison of Sohag 

 was also in attendance. Moktah Bey, as usual, acted as 

 interpreter, and the final arrangements for the eventful 

 day were made. First among these the military guard 

 had to be largely strengthened, for not only is a very 

 pardonable curiosity a thing to be utterly suppressed 

 during eclipses, but a whisper had gone abroad that the 

 False Prophet of the Soudan had included the eclipsers in 

 his anathemas, and even one fanatic in the camp at Sohag 

 might give a deal of trouble. And at last the 17th came, 

 ushered in by the finest morning we had had — (clouds had 

 been terribly persistent for several previous days at the 

 time the eclipse was to happen) — and when the observers 

 turned out at dawn to put the final touches to their pre- 

 parations the local excitement had begun to show itself. 

 On the hill, under palm trees, between us and Sohag 

 there was already a great crowd, which rapidly increased ; 

 but a cordon of sentries round the camp kept everything 

 quiet within. 



And now for the actual work. In an eclipse there are 

 four critical points : the first, second, third, and fourth 

 contacts, so called — the first when the moon makes its 

 appearance on the sun, the second when its first totality 

 obscures it, the third when the sun again reappears, and 

 the fourth when the sun is quite clear of the moon again. 

 It is of course with the totality — that is, the time that 

 the sun as we know it is invisible between the second 



and third contacts— that the physical astronomer has 

 almost exclusively to do, but as some of the phenomena 

 are visible slightly- before totality the time has to be 

 carefully watched. During totality this has to be done 

 in the most steady manner, and the observer upon 

 whom this duty falls has a most responsible task. Tn 

 the English observatory, to which I shall now confine 

 myself, this fell upon Mr. Buchanan ; and as the ar- 

 rangement adopted this time was new, I will describe it. 

 It was devised by Mr. Lockyer as the result of his Indian 

 experience, when the timekeeper found it so difficult to 

 keep the time and to observe the eclipse, which he had 

 come 600 miles to see, that he resolutely turned his back 

 upon the sun lest he should fail in his self-imposed task 

 and so disturb the work of others. What one wants to 

 know at any moment during an eclipse is for how many 

 seconds the phenomenon is yet to be visible and when 

 each ten seconds of the totality have flown away, as 

 each observer has generally more than one thing to do, 

 and the announcement of the timekeeper is the signal 

 for changing his instrument. On this occasion a clock 

 used for testing gas meters was employed, with a seconds 

 pendulum set going at the moment of totality, and with 

 a large dial marked 65, 60, 50, 40, and so on to o; 65 

 being the number of seconds which it was thought would 

 leave a safe interval for covering the lenses of all the 

 cameras before the actual termination of the eclipse. 

 The plan answered admirably. Mr. Buchanan sang out 

 the times shown on the dial, and sketched the eclipse 

 with perfect ease. 



While the land was darkening and the sky and the Nile 

 were beginning to put on those indescribable hues round 

 which so much of the terror of eclipses is centred, and 

 while the whispers on the hill at Sohag were beginning to 

 surge into a sjund— half roar, half moan- some eight 

 minutes before totality, Mr. Lockyer announced the ap- 

 pearance of bright lines, indicating that our atmosphere 

 was already dimly illuminated enough to permit of the 

 atmosphere of the sun being seen through it, and it was 

 easy to see by the rapid pencilling on a copy of Angstrom's 

 map, which was arranged on a stand under the eye-piece 

 of his spectroscope that observations in earnest had com- 

 menced. This went on, the image of the retreating cusp 

 of the sun being carefully kept on the slit of the spectro- 

 scope, by Mr. Lawrence until Dr. Schuster, as had been 

 arranged, announced the instant of totality. At this 

 signal Mr. Buchanan said, " 65 seconds," Mr. Lockyer 

 left the spectroscope to study the structure of the corona 

 with the telescope, and Dr. Schuster uncovered all the 

 lenses of his camera— all four of them arranged on a 

 single stand— and to all, except the observers, the sun's 

 atmosphere shone out in all its splendour and majesty, 

 and the roar increased on the hill. In the telescope the 

 verdict was that the solar conditions of 187 1 were again 

 present ; and at the signal " 40 seconds more," the infor- 

 mation to be gathered by the naked eye and the gratfng 

 was to be sought by one observer, while the photographic 

 plates had to be changed by another. At this moment 

 the silence in the observatory was broken bv shouts 

 calling attention to a strange object among the fainter 

 exterior details of the corona itself, which were more sus- 

 pected than seen. There, one solar diameter to the right 

 and one solar diameter long, was an exquisitely formed 

 comet, complete with nucleus and tail, sweeping in a 

 beautiful curve, in brilliancy almost, if not quite, equalling 

 that of the very corona itself— a real photometer, in fact, 

 of which we have not yet heard the last. As in the naked 

 eye view there was a struggle with the comet, so with the 

 grating there was a struggle of another kind. A prism 

 or a diffraction grating used without lenses forms what is 

 called a slitless spectroscope. The coronal ring is really 

 used as a circular slit, and according to the substances 

 present in the solar atmosphere we shall have rings or no 

 rings ; and if rings are seen, then their presence in 



