the sixth nervure is wanting in the specimen, but undoubtedly divides at its origin. The outer branch forks a short distance from the margin, and the outer of these branchlets, and probably the inner also, again fork very near the margin. The inner branch forks about the middle of its course, both these secondary branches forking once or twice.

All the interspaces are filled by a finely reticulated and very delicate net-work of minute nervures, but there are no straight cross-nervures. There is, however, a series of nervures running from the second nervure to the anterior margin, which are stronger than the general net-work, but still seem to be a part of it.

This wing differs so much in neuration from any family of recent insects, that it is difficult to point out any near affinity with living forms, although it shows some points of resemblance to several families of Neuroptera, and especially to the Ephemerids. To Hemeristia and Miamia, described and figured by Prof. Dana* and Mr. Scudder,† from the Carboniferous formation at Mazon creek in Illinois, it shows more resemblance, but still differs more from either of these genera, which are considered distinct families by Mr. Scudder, than they do from each other. From the forms described by Mr. Scudder in the third volume. of the Geological Survey of Illinois, it is even more widely separated.

To the species described from the European Carboniferous, it seems to be still more closely allied. Prof. Hagen, to whom a tracing of the specimen was sent, is of the opinion that it will be found to belong to the same genus as the Dictyoneura libellu loides of Goldenberg. Prof. Hagen, also, regards the remarkable Eugereon Böckingi Dohrn, which has attracted so much attention, as the same genus, and perhaps the same species, as D. libelluloides. In both Dictyoneura and Eugereon, as figured, the wings have considerable resemblance to the specimen from Indiana, but in neither of them are the nervures so numerously branched toward the posterior border of the wing, and in Eugereon the spaces between the three first nervures next the anterior border are connected by straight cross-nervures. There are also important differences in the branching of the main nervures. Regarding these differences as at least of generic value, I propose to institute a new genus for the species from Paoli, and call it Paolia vetusta.

*This Journal, vol. xxxvii, pp. 34, 35, figs. 1, 2, 1864.

This Journal, vol. xl, p. 268, 1865, and Memoirs Bost. Soc Nat. Hist., vol. i, p. 173, pl. 6, 1866.

Die fossilen Insecten der Kohlenformation von Saarbrücken (aus den Palæontographicis von Dunker und Meyer, Band iv, 1854), pl. 1.

Eugeron Böckingi, eine neue Insectenform aus dem Todtliegenden (aus Palæontographica von Dunker, Band xiii, 1866, pl. 41.

ART. X.-Earthquake of October 20th, in Northeastern America; by ALEX. C. TWINING.

NOTICES of the earthquake of October 20th last, collected from the newspapers and received from other sources, display an area of disturbance extending from New Brunswick in the East, to the State of Iowa in the West, and from the Lakes and the River St. Lawrence in the North, to Cincinnati and Richmond, Va., in the opposite direction. No doubt the actual area of disturbance was far more extended, especially in the East and North; for the manifestations were at least as strong in degree at the utmost bounds of our information in these last directions, as in those parts with which we are most immediately familiar. The same conclusion is confirmed by the circumstance that, even where the motions were most fully developed, they were not obvious to persons not favorably situated for receiving impressions from them. It is easy to believe that they escaped public attention over large regions where they took place sensibly, although but feebly.

At this place-New Haven, Connecticut-the movements, both in the precise time of their occurrence and in the attendant circumstances, were immediately and critically investigated by the writer, from the testimony of many intelligent citizens. Independently, and in their various situations and positions, the witnesses agreed in describing an oscillatory movement, to and fro, in the general direction of N.N.E. to S.S. W.,-not level but rocking. This last sensation is plainly indicative quite as much of a vertical displacement, combining irregularly and oppositely with the horizontal, as of any alternations of inclination in the earth's surface, after the manner of a wave, and a consequent vibratory condition of persons and objects. Still, that the latter did take place is a conclusion that seems to be made inevitable, by the invariable fact that the oscillations were by far the most perceptible in lofty situations,--for example, in the ascent progressively from the lower floors of edifices to the upper stories. In the latter, at least, objects were both felt and seen to be in motion; and suspended objects, as lamps and pictures, were set into vibration, with a range of three or four inches and, when free, in the direction already specified. There were two distinct shocks. In estimating the duration of these and of the interval between them, and also in estimating their component oscillations, these durations and intervals were in no case recorded from mere verbal statements, but means were employed to ascertain the informant's mental impressions and recollections, applying to them my own measurement, as to time.

These impressions and recollections would often give durations more than double, in some instances, of the like in other instances. Taking, however, the most trustworthy, and allowing to the others a weight proportioned to their value, under the circumstances, the first shock was found to have continued through about nine seconds, the second through about eleven seconds, and the interval about five,-making, altogether, twenty-six seconds. The time of each double vibration-that is both to and fro-was concluded to approximate to a second and onethird, although, so far as mere numbers were concerned, the witnesses more generally approved not more than one second, or even less. The precise time of day will be referred to farther on. It is remarkable that motions which were not even noticed, ordinarily, by persons in basement stories or in the streets, should have produced in most of those who felt them nausea or dizziness or other affections, according to the temperament of the individual.

A careful comparison of the various newspaper paragraphs which have come to hand-nearly forty in number-makes it clear that the general phenomena were everywhere the same. Every where there were two shocks experienced of a few seconds each, and a brief interval. These are about as variously stated in duration by the newspapers as the same were stated by dif ferent observers at New Haven-thus, at Troy 15 to 20 seconds in all, at Montpelier 30, at Cleveland 15 to 30, the prevalent authority being for the latter, at Boston 18 to 30, at Brunswick, Me., 30 to 40, at Cincinnati 30 and less, at Hartford 20 to 60, at Cornell University, Ithaca, three shocks of 15 seconds eachthe three being too exceptional among the mass to be credited, and having but one other parallel, that is, Brooklyn. At Harvard College Observatory the duration of tremor was from 8 to 15 seconds by the estimate of different observers,-two shocks with a continuous tremor between, and the component oscillations 40 in a minute according to observer W. A. Rogers. At East Saginaw, Mich., the first shock is described as 10 seconds, then an equal interval, then a second shock of 10 seconds. very few of the statements are so abnormal, one or two in their brevity (one or two seconds) and about as many in their length (two or three minutes), that no weight can be accorded to them. On the whole, the entire duration-26 seconds-at New Haven, is confirmed as having been about the duration in all other places observed—a uniformity probable in itself. In one instance the oscillations are spoken of as four or five in a second, and as being like the motions of a boat,-also in one other (at Keene) they are described as having been vertical.

A

Respecting the relative amount of disturbance at different places, the sensations experienced by individuals would be but

a fallacious test, because so much influenced by temperament, as well as by situations and positions. Persons sitting, for example, were far more sensitive than persons standing. Again, while operatives in upper rooms often rushed down-as here at New Haven-in a panic, persons standing or walking in the immediate vicinity below, did not even perceive the phenomenon. The same remark applies to the reported swaying of walls and buildings ten inches to a foot, which is no doubt exaggerated in amount. But a vague conclusion may be derived from specific occurrences, such as the displacement of objects, the cracking of window panes or of ceilings, and the falling of chimneys, as well as from the degree of public notice which the event excited. All that, in the present instance, can be rationally deduced from such indications would seem to be that the amount of disturbance at New York, at Cleveland, at Milwaukee and Detroit was about the same as at New Haven; that it was greater at Boston, at Brunswick, at Montreal and at Quebec; that it was less at Cincinnati, at Chicago, and at Dubuque, and was but just distinctly perceptible at Richmond, Va. In other words, the movement was more remarkable in the East and North, and less in the West and particularly in the South. It is also believed that no like occurrence comparable in the aggregate with this one has been experienced in New England during the present century, nor since November 18, 1755supposing the newspaper quotation, relative to that event, made by a Boston correspondent, from "a book published in 1786" to be correct and authentic.

It only remains to compare the times noted at the various places concerning which our information is sufficiently authentic. At this place there were two among the observers who separately noted the time by reference to standard time-pieces. By each the same time of beginning was given, within a few seconds;— that is, 11h 19m 46. The average of three other observations by time-pieces whose errors could not be ascertained except on the day after, proved to be very nearly the same. The same conclusion was farther confirmed, with sufficient exactness, by the average of three clocks which had stopped, as observed upon their dials. Prof. C. Smallwood of Montreal Observ'y has obligingly furnished observations of local time in the Canadas which are entitled to confidence, viz., at Quebec, Montreal and Owen's Sound, and also at St. Johns, N. B. These will be found in their place in the table below. The time at Boston, taken by Mr. Farmer with care, is communicated by Prof. Newton, together with most of the newspaper notices herein referred to. That at Harvard College Observatory has been obligingly furnished to the writer by Assistant Arthur Searle, together with the other facts herein stated as observed at that locality. The AM. JOUR. SCI.-THIRD SERIES, VOL. I, No. 1.—JAN., 1871,

time at Cleveland, Ohio, is the average of three clocks that were stopped, and is confirmed essentially by Col. Whittlesey, but without an actual reference of either to a standard time-keeper. From these combined the following table is composed; of which column 1 gives the place of observation; column 2, the latitude; column 3, the difference of local time from New Haven corresponding to the longitude; column 4, gives the respective local times corresponding to 11h 19m 468-the beginning at New Haven; column 5, is an empirical scale of progress proportioned to the differences of longitude and the presumed differences of absolute time at St Johns and Chicago; column 6, gives the observed times of the earthquake; column 7 is comparative of the two preceding, and shows the presumed error of observation, whether too late or too early at each of the places respectively. It would obviously only obscure the discussion to take account in the table, of times which do not purport in the notices themselves to be near approximations, or which are adopted from the railroad time-pieces without supplying the proper correction, or which are found by comparison with the mass of observations to be grossly in error. To one or the other of these categories belong the notices from Brunswick and Portland, Me., Burlington, Vt., Warrensburg, Saratoga, Cooperstown, Cornell University, and Auburn, N. Y., Scranton and Titusville, Pa. The notice from Cincinnati, Ohio, is retained on account of the extreme position.