Commencing at noon in Alaska, the line of totality ran through British America, passing through the south-west corner of Minnesota diagonally through Iowa, crossing the Mississippi near Burlington, thence through Illinois, West Virginia, and North Carolina, and entering the Atlantic Ocean on the North Carolina coast, near Beaufort. The path of the eclipse through the more inhabited parts of the continent literally bristled with telescopes; the whole line being converted into one vast observatory. Although the duration of totality was less than in India last year, the circumstances were more favourable for observation, the heat being less and the position of the sun more convenient for observation, instead of being almost vertical. The principal points which had to be observed were the nature of the protuberances, examined with the spectroscope and recorded photographically; the nature of the corona; and the detection, if possible, of any intra-Mercurial planet. As might be expected from the easy accessibility of the entire line of totality, this eclipse has been most thoroughly observed by numerous parties, the report of whose work will in due time be presented to the scientific world.

The most important observations were those recorded by the Iowa expedition, towards the expenses of which 5000 dollars had been voted by Congress. The writer has to thank his friend, Dr. Henry Morton, Professor of Chemistry in the University of Pennsylvania, who had the superintendence of this expedition, for full details of the results obtained, together with some exquisite photographs of the phenomena of totality, &c. These pictures show, in the first place, very fine definition in the telescope employed, as the roughness or mountainous character of the moon's edge is clearly given in the pictures of partial phase, as well as the sun-spots and surrounding faculæ.

The telescopes which were available for the purpose were two fine Munich Equatorials, of 6 inches aperture, with clockwork, and also an excellent Dolland, of 4 inches aperture, equatorially mounted, but without clockwork. It was concluded that on account of the risk of local clouds it would be desirable to take all these instruments, and distribute them over some distance on or near the central line, and it was also considered that at least five skilled operators would be necessary to each instrument. The next important point was the choice of the party, and it was soon found that an excellent selection might be had from among those whose position or engagements would allow them to volunteer without other compensation than the moral one contingent on success; and after a few changes, rendered necessary by sickness or other inevitable cause, the party as finally constituted consisted, besides Professor Morton, of Professor A. M. Mayer, Ph.D.; Professor C. F. Himes, Ph.D.; Messrs. J. Zentmayer, O. H. Willard,

E. L. Wilson, H. C. Phillips, E. Moelling, J. C. Browne, W. J. Baker, James Cremer, H. W. Clifford, O. H. Kendall, J. Mahoney, and W. V. Ranger.

It was a question of some moment to decide whether, for obtaining the photographic records, they should follow the plan adopted by the French and German expeditions of last year, and take the photograph in the principal focus of the object-glass, thus securing great intensity of light in a small image, or follow the method employed by Dr. De la Rue in 1860, when he used an ordinary Huygenian eye-piece so placed as to produce an enlarged image of the first image from the object-glass. It was found by experiment that with a clear sun it was necessary to reduce the aperture of the telescope (which was 4 inches, and 50 inches focus) to 1 inch, and to use a diaphragm slide of th inch aperture, in order to get a proper exposure when the solar image was enlarged from 6 inch (its diameter at the principal focus of the objective) to 2 inches on the ground glass. The same size of aperture was adopted for the larger instruments during the partial phases, the entire aperture, in all cases, of course being used during totality.

The work of designing and constructing these lenses, and also the different attachments to the cameras for securing exposures of various degrees of rapidity, from a very small fraction of a second to any desired length, was placed in the hands of Mr. Joseph Zentmayer, whose extended scientific attainments, combined with unrivalled skill in the construction of optical instruments, peculiarly fitted him for such a task.

As the operation of the eye-piece, when employed to produce an image on the screen or ground glass of a camera, is essentially different from that which it performs in its usual office, it was judged best by Mr. Zentmayer to make some alterations in its form. Thus, in the first place, since in the present case the "eyelens" of the eye-piece undoubtedly makes a secondary image of the primary image formed within the eye-piece by the combined action of the objective and the field-lens of the eye-piece, it is clearly desirable to make this lens of a longer focus than usual, so that its errors may be of less account. It was also essential to give the new eye-piece a wide angle, so as to secure a sufficient field not only for the solar disc, but also for the corona.

While therefore the ratio of focal lengths in the two lenses of the ordinary eye-piece is usually 1:3, it was in this case as 1:2. While the distance between the lenses is usually the sum of their focal lengths divided by 2, it was here made equal to the sum of the focal lengths divided by 2, plus 24 inch. This was to give space for the introduction of the reticule of spider lines, which would otherwise have been brought too near the field-lens, and also

to keep this lens beyond the conjugate focus of the eye-lens, as otherwise particles of dust on the former would have been too faithfully portrayed by the latter.

The elements actually adopted were as follows:

Equivalent

0 1.75

Distance of reticule from eye-lens for 5-in. distance) 0 1-62

of ground glass..

When the instruments were boxed and packed, it was found that, with the various photographic appliances, they made no less than five furniture-car loads of material.

In arranging the division of the party into three sections, with the three telescopes, so that they might be distributed along the line of totality, and thus diminish the chance of universal extinction by local clouds, Professor Morton was chiefly guided by the desire of securing in each section such a diversity of special ability as might make each self-dependent and complete; also, to leave nothing undone to secure content and harmony of feeling. He assigned to himself the University telescope, which being of smaller size and without clockwork movement, could not be expected to do as good work as the others: though should they by chance be overclouded, its result would be invaluable.

The High School telescope, 6-inch aperture, 9 feet focal length, was under the charge of Professor A. M. Mayer, Ph.D., and Mr. O. H. Kendall. It was stationed at Burlington, 40° 48′ 17′′ N., Oh. 56m. 13s. West of Washington. By, measurements of the photographs taken by this party, Professor Mayer has shown a change of shape in one of the larger spots during the eclipse, amounting to a motion of 2000 miles, in its edges.

The Gettysburg telescope, 6-inch aperture, 8 feet focal length, was in charge of Professor C. F. Himes, Mr. J. Zentmayer, and Mr. E. Moelling. This was stationed at Ottumwa, about 75 miles nearly west of Burlington.

With the University telescopes were Mr. E. L. Wilson and Professor Morton. This section was placed at Mount Pleasant, between the other stations.

It is almost needless to say that all officials connected with the railways acted with the greatest liberality in transporting the apparatus and observers to the selected sites.

The various parties having reached their destinations, arrangements were at once made to get the instruments into position. In

the case of the Burlington party, all went smoothly, and the dark weather alone prevented final adjustment until the night of the 6th, or morning of the 7th, when this was secured by Professor Mayer, who sat up all night for the purpose.

With the Ottumwa instrument it was, however, found that the clockwork had become seriously deranged in carriage, so that Mr. Zentmayer was obliged to take it entirely apart and refit it. The final adjustment was only given to this instrument during the morning of the 7th by Mr. Zentmayer, who had watched all night, vainly, for a star.

The telescope at Mount Pleasant having no clockwork, and being otherwise unfit for any fine adjustment, required no arrangement except what could be given during the morning of the 7th.

The weather on the eventful day of the eclipse was at all stations perfect, thus rendering needless the policy of distribution, and no less than 116 negatives were taken, including 13 during totality, showing a large number of prominences, some massive and others delicate as well as radiant brushes of a softer light, such as have been before seen, but never as yet photographed. By another of the sections of this large party, beside similar pictures to the above, one was obtained showing the curious phenomena known as Baily's beads, being simply the last glimpse of the sun's edge cut by the peaks of lunar mountains into irregular spots. The time of exposure determined by Professor Mayer for the partial-phase pictures was the th of a second. Those taken during totality were exposed from five to sixteen seconds.

The general character of the prominences will be seen by the coloured illustration, which has been excellently copied from the original photographs and micrometric measurements forwarded to us by Professor Morton. The dotted circle inside the circumference of the moon, shows the relative diameter and position of the sun at the middle of the total eclipse. The accompanying woodcut may be regarded as a key to the coloured picture, and will serve to facilitate the following description of the phenomena:

The line A B represents the direction of a parallel of declination. CD a declination circle. FE is the moon's path from first contact at F. The prominences are here all shown at once; although, of course, those on the sun's eastern limb alone were seen at first, those on the west side only at the end of the totality. Proceeding from the north to the east, we first meet with a small prominence having the position angle of about 56' 30'; it is of the shape of a rice grain, with its base but slightly below the circumference of the In breadth it is 2° 50', and in height 22"; as 1' on the circumference of the sun equals 124 miles, and 1" of arc of the sun's distance on August 7th subtends 449 miles, it follows that its actual dimensions are 21,000 miles long and 9900 miles high.

moon.