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5. Although, in the preceding drawings, I have represented this unilateral widening exclusively on the more refrangible side of D, I have observed it on the other, though scarcely so frequently.

6. Accompanying these appearances, but generally best visible when the absorption with curved boundary is visible on both sides of D, is a brilliant boundary replacing the mere change of shade.

7. At times the brilliant boundary is continuous across D, as shown in fig. 6; but I append figs. 7 and 8 to show that the phenomena on either side of D are independent of each other.

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8. At times, D puts on the appearance of the limiting line of a channelled-space spectrum, the "easing off" of the absorption being now on one side and now on the other.

9. Should all these phenomena be ultimately referred to the causes which produce a channelled-space spectrum (one of which undoubtedly is the tendency to a unilateral instead of a bilateral widening), a line-spectrum will be regarded as a special case merely, and not as an entirely different spectrum, as it has been hitherto ; and the range of molecular combinations in any one element from which line-spectra may be produced is extended.

10. The question further arises, whether many of the short lines in spectra are not remnants of channelled-space spectra.

June 18.-Joseph Dalton Hooker, C.B., President, in the Chair. The following communication was read:

"Researches in Spectrum-Analysis in connexion with the Spectrum of the Sun."-No. IV. By J. Norman Lockyer, F.R.S.

Maps of the spectra of calcium, barium, and strontium have been constructed from photographs taken by the method described in a former communication (the third of this series). The maps comprise the portion of the spectrum extending from wave-length 3900 to wave-length 4500, and are laid before the Society as a specimen of the results obtainable by the photographic method, in the hope of securing the cooperation of other observers. The method of mapping is described in detail, and tables of wave-lengths accompany the maps. The wave-lengths assigned to the new lines must be considered only as approximations to the truth. Many of the coincidences between lines in distinct spectra recorded by former observers have been shown, by the photographic method, to be caused by the presence of one substance as an impurity in the other; but a certain number of coincidences still remain undetermined. The question of the reversal of the new lines in the solar spectrum is reserved till better photographs can be obtained.


[Continued from p. 243.]

May 27th, 1874.-John Evans, Esq., F.R.S., President,

In the Chair.

The following communications were read:

1. "On the last Stage of the Glacial Period in North Britain." By T. F. Jamieson, Esq., F.G.S.

In this paper the author arranged the Glacial phenomena of Scotland under the following three heads :

1. The great early glaciation by land-ice (maximum effects of glaciation).

2. The period of glacial marine beds containing remains of Arctic Mollusca, when most of the country was covered by the sea.

3. The time of the late glaciers, the special subject of the paper.

After expressing himself in opposition to the hypothesis of a great polar ice-cap, the author described this last period as one not of mere local glaciers, but as characterized by a return of a great icesheet over nearly the whole of Scotland and Ireland; but he stated that this ice-sheet was probably neither so thick, so extensive, nor so enduring as that of the first period of glaciation, which cleared away every thing in the shape of superficial deposits down to the hard rock. He believed, however, that in the last period the mountains of Scotland and Wales, as well as the Pennine range and the rest of the north of England as far as Derby, were covered with thick ice, which in most parts reached down to the sea, and that extensive snow-beds prevailed over the rest of England. In the summer months the melting of these would give rise to streams of muddy water, and produce the superficial deposits of Brick-earth, Warp, and Loess; whilst, when the currents were stronger, perhaps from the thaw being unusually rapid, deposits of gravel would be formed. This second ice-sheet would gradually become less and break up into valley-glaciers, which in their retreat would leave kaims and eskers at low levels, and moraines in the mountainglens. During this time no new great submergence of the country took place; and the last great modifications of the surface were subaërial, and not submarine, the work having been done by frost, rain, and glaciers.

2. "Notes on the Upper Engadine and the Italian Valleys of Monte Rosa, and their relation to the Glacier-erosion Theory of Lake-basins." By the Rev. T. G. Bonney, M.A., F.G.S.

The author stated that he had examined :-(1) the small lakes on the summit of the Bernina Pass. These were situated in a position very favourable to glacier-erosion, and, he thought, might be attributed to that cause. (2) The lakes on the upper part of the Maloya Pass. These lay in three rock-basins, and at first sight seemed favourable to the glacier-erosion theory; but further examination showed that they were in no way connected with the glacial system of the neighbourhood, and were probably preglacial. (3) The Val Bregaglia to the Lake of Como. The presence of barriers in the valley, its frequent V-like form, and the signs of glacial action to near the present level of the stream, seemed to indicate that the glacier had had but slight erosive power. (4) The Como arm of the lake. It was shown that the glacier which was supposed to have excavated the lake had passed over the ridge of Nagelfluhe and Molasse that encloses it, and had not been able to grind away its remarkably sharp crest. (5) Similar evidence was produced with regard to the Lake of Orta. (6) The Italian valleys E. of Monte Rosa. These were shown to offer difficulties precisely similar to those of the Val Bregaglia. The author therefore argued that these cases showed how superficial the action of the glaciers had been, and that they must have been wholly inadequate to excavate the greater lake-basins,

since no approach to this form, no U-like trough, was found in the valleys down which the glaciers had flowed on their way to the lakes. As, then, the principal features of the district appeared to be preglacial, he contended that disturbances of the beds of the valleys along lines transverse to their direction were more likely to have produced the lakes.

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June 10th, 1874.-John Evans, Esq., F.R.S., President,
in the Chair.

The following communications were read:

1. "On the occurrence of Thanet beds and of Crag at Sudbury, Suffolk." By William Whitaker, Esq., B.A., F.G.S.

After referring to some passages in papers by Mr. Prestwich, in which the probable existence of Thanet beds in North Essex is mentioned, the author described certain sections near Balingdon, on the right bank of the Stour, which exhibit sands belonging to this series. The principal section at the Great Chalk-pit, Balingdon, shows, in descending order, beds belonging to the London Clay, Reading beds 9 feet, and Thanet sands about 14 feet, resting on Chalk. No fossils occur in the Thanet beds; and their identification is founded on the uniformity in the character of the sands, their resemblance in fineness, compactness, and colour to the Thanet sands of West Kent, the presence at the base of the series of a greensand resembling the "base-bed" of the Thanet sand, and the occurrence immediately beneath it of a layer of tabular flint, as is usual where the Thanet sand caps the chalk.

The Crag-beds described by the author are found on the left bank of the Stour, in Suffolk, and consist of ferruginous dark reddishbrown sand, with layers of ironstone, slightly false-bedded, with here and there light-coloured grit with broken shells. In the lower part there are layers of flint pebbles, phosphatic nodules, and phosphatized bones, which also form a bed about 1 foot thick at the bottom. These beds rest on deposits belonging to the lower portion of the Thanet sands, and these again on the Chalk. In one pit a considerable number of fossils occur, but not in a condition to enable them to be satisfactorily determined. From their position and general characters these beds were referred by the author to the Red Crag.

2. "Note on a modified form of Dinosaurian ilium, hitherto reputed Scapula, indicative of a new genus, or possibly of a new order of Reptiles." By J. W. Hulke, Esq., F.R.S., F.G.S.

The author reexamines Mantel's " Scapula of an unknown Reptile"=Owen's "Scapula of Megalosaurus?", and adduces reasons for considering it to be a modified Dinosaurian ilium. He describes two new examples of the bone in Dr. Wilkins's collection, contrasts them with undoubted scapula of sundry Dinosaurs and existing reptiles, and proves their essential correspondence with the ilia of known Dinosaurs.

3. "Note on a Reptilian Tibia and Humerus (probably of Hylaosaurus), from the Wealden Formation in the Isle of Wight." By J. W. Hulke, Esq., F.R.S., F.G.S.

In this communication the author describes two saurian limbbones, remarkable for the great expansion of their articular ends, and the shortness and smallness of their shaft. The features of the tibia are more like those of the tibia of Hylaosaurus than of any other Dinosaur. This resemblance, and the suitability of the humerus to the very massive articular end of the Hylæosaurian scapula, dispose the author to refer the bones to this Saurian.

XXXVII. Intelligence and Miscellaneous Articles.


THE magnetic moment of a magnetized needle may always be regarded as the product of two factors, of which the one expresses the quantity of magnetism contained in the needle (or, if preferred, the power of each pole), while the other factor is equal to the distance of the poles. By the advice of M. Jamin I applied myself to determine these two distinct elements separately, and to study apart the variation of each of them when the conditions of magnetization are changed. The following is the principle of the method employed.

It is easy to verify that the magnetic moments y of a series of needles of different lengths, magnetized under the same conditions, can be represented by a formula such as

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provided that their lengths exceed a certain limit 7. In all these needles the quantity of magnetism is constant and equal to m, and the distance of the poles from the extremities is also constant and equal to. If we break these needles and take from their middle parts various fragments of lengths exceeding another limit l'<l, their moments y' are represented by the formula

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the quantity of magnetism is the same as in the mother needle; but the poles are nearer to the extremities, & being always less than d. These facts, almost evident à priori, have been carefully verified by experiment.

Suppose now that m and d are to be determined for a given needle. We first ascertain its magnetic moment y; it is then reduced by the removal of a sufficient length from both ends, and the new magnetic moment y' determined. We know that in ruptureneedles of the same diameter the quantity & is constant, whatever the intensity of the magnetization; its value, known beforehand, is, for instance, 5.5 millims. in needles of 0.553 millim. diameter. "Studies on Magnetism," III., Phil. Mag. March 1875, pp. 188-191. Phil. Mag. S. 4. Vol. 49. No. 325. April 1875.

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