the atomic weight of nitrogen, we shall still have a number conforming to the character of the series, viz., 89.

In this and the following series the symbol M' represents a possible metal constituting an intermediate term between antimony and bismuth. That such a metal might exist was pointed out in the consideration of the phosphorus series.

M as before represents an hypothetical metal having for its atomic weight a mean term between those of silver and gold.

The parallelism between the three first terms of these last two series commencing respectively with molybdenum and magnesium is positively exact, perhaps the only known case in which absolute exactitude obtains. It is probable that other cases of parallel series exist, and will be discovered.

It is not easy to fix the exact amount of importance which attaches to the numerical relations up to this time ascertained to exist between the atomic weights of the elements. Some are no doubt mere casual coincidences, and relations remarkably exact and symmetrical may exist between the atomic weights of bodies which have no analogies in their properties: for example we may take calcium 20, selenium 40, uranium 60, bromine 80, mercury 100. Here the differences are not only exact, but all the subsequent numbers are multiples of the first, and this between bodies remarkably dissimilar in their properties-a striking proof of the necessity of caution in inferring relations of properties as following from relations of numbers. But on the other hand, to reject the relations of number when accompanied by analogy of properties, as unmeaning and unimportant, would be to err quite as much on the other side. When the received equivalent of an element forming a term in a well marked series differs from that obtained by calculation, it naturally leads, as Prof. Mallet has remarked, to suspect an error and desire a redetermination. The fact that a group of elements allied in their chemical characters may be arranged in a series having a common difference or a definite ratio between its terms, confirms the propriety of grouping those elements together, and such analogies may in doubtful cases assist us in arriving at a correct classification.

Philadelphia, Feb. 27, 1860.

ART. XXXII.-Ornithichnites, or tracks resembling those of Birds; by ROSWELL FIELD, of Greenfield, Mass.

WHEN fossil footprints were first discovered in the sandstones of the Connecticut Valley, it was indeed thought to be a great discovery, but that the tracks, thus found were made by birds was received by men of scientific attainments with great distrust and skepticism. That they were tracks made by once living animals there could be no doubt, but that they were ornithichnites was very much doubted.

It was not indeed until after my esteemed friend Dr. Hitchcock had spent much time in comparing, describing, and in distributing specimens, that the scientific public became satisfied that they were the tracks of once living birds.

The great and only proof that they were the tracks of birds, is found in the organization of the fossil foot, in the numbers of joints or lateral expansions in the toes; in this they are supposed to agree, and probably do, with living types; this with alternate steps of right and left feet is all the evidence we have that they were the tracks of birds.

Living in the immediate vicinity of Turner's Falls, the locality that has furnished the most numerous, and beyond all comparison the most beautiful specimens, my attention was drawn many years since to this particular subject. It was from my farm that the late Dexter Marsh obtained his choicest specimens. And it was in the vicinity of these Falls where my much lamented friend Dr. Deane found "new walks in an old field:" Where our barren and rocky wastes became to him a garden of delight.

It was here I witnessed their labors with pleasure, and in a more obscure way have followed in their footsteps. I think I may safely say that I have uncovered more footprints, and found more new species, and a greater variety of tracks than any other man, I think I might also say with propriety than all others that have preceded me, and if I have learnt anything on this subject I have learnt it at the quarries. It is there, and there only I have studied the history of Triassic days, and the more I have studied, the greater have been my doubts as to the ornithic character of of the tracks which these tables of stone contain. I have seen thousands of tracks that others have not seen. With injudicious blasting, and the carelessness of workmen many choice specimens have been broken and lost; other slabs literally covered with footprints, have been spoilt by suncracks the shrinkage of the mud in drying; the stratum over which the animal moved being either too hard or too soft to receive or retain good impressions, all such are rejected and lost to the student, at the quarries.

any

SECOND SERIES, VOL. XXIX, No. 87.-MAY, 1860.

I have no new theory to advance, and none to build up, but if I can rightly decipher these fossil inscriptions impressed on the tombstones of a race of animals that have long since ceased to exist, they should all of them be classed in the animal kingdom as Reptilia. If I have not studied this subject in vain they were all quadrupedal. That they usually walked on two feet I admit, and that they could as readily walk on four when necessary is equally true. In proof of this we find tracks as perfect as if made in plaster or wax, which to all appearance as to the number of toes, and the phalangeal or lateral expansions in the toes agree perfectly with those of living birds, and still we know by the impressions made by their forward feet that these fossil tracks were made by quadrupeds. In other cases where the animals sunk deep in the muddy stratum over which they moved, it is plain that they dragged their tails in the mud, leaving a groove plowed up from one half inch to an inch in width. This groove is not always found on the surface where the foot rested, the weight of the animal causing the foot to sink through the yielding stratum, whilst the tail dragged on the one above. This we know was the case with animals that were surely quadrupeds, but they show the appendage of a tail only when their feet sunk deeply in the plastic clay. Thus the proof that we once relied upon to prove them birds can be relied upon no longer.

That there were quadrupeds in those sandstone days and that these had hind feet perfectly agreeing with the stony birdtracks, throws great doubt and distrust on the question, whether there were any true birds in this age of reptiles.

If there were birds they were doubtless apterous and naked, for we should naturally suppose that where so large a number of birds congregated upon the muddy banks, that in dressing and pluming their feathers some of them must have been trodden under foot, but the impression of feathers has never been found, although we find the smallest leaves of vegetables, and the pathway and tracks of annelids, and insects, some of them so small that they can hardly be seen with the naked eye. Even the Otozoum whose giant-like track measures twenty inches in length, once supposed to have been a biped reptile, by later discoveries is proved to have been four-footed. Other new discoveries have reduced the number of so-called birds, transferring them to the class of quadrupeds, which I.verily believe is the proper place for all of them. The smoothness of the bottom of the foot in our fossil tracks agrees better with some species of batrachians that now live in and about the water, than it does with such animals as live on the land. Had birds existed at this early geological period, when the sandstone of the Connecticut valley was being deposited, there has indeed been a woful gap in their history, from then up to near the historical period, while the die from

which they were struck at their creation was not broken, but a new edition produced in these latter days. The work perhaps may have been revised but has not been enlarged as respects the size of the animal. I know that many eminent men and men of great scientific attainments, men who have spent much time and labor for many years in the investigation of this subject have come to different conclusions, and it may not become me to say that their conclusions are wrong. I would only add that when fossil tracks were first discovered there was so little known of the formation of the feet of fossil or of living animals, and particularly of their footprints that it is possible the first discoverers might have been mistaken as to the ornithic character of the footprints. The study of these fossils so very interesting to the geologist and naturalist, still merits their earnest attention. There is no known locality where they are found in such abundance, and in such perfection as at Turner's Falls, the northern terminus of the sandstone beds. Very few indeed have any conception of the marvelous perfection of this fossil inscription, or of the multitudes of once living creatures whose existence they commemorate.

March, 1860.

[Mr. Field is a plain farmer, who makes no claim to be an authority in science, but like Hugh Miller has hammered his geology out of the rocks on which he lives. He is well known as one of the most successful collectors of the foot-marks of the Connecticut sandstone, and his testimony as to the impression made on himself of their probable character and origin, has the merit of a conviction making head in an honest mind against all the weight and bias of opposing authorities.-EDs.]

ART. XXXIII.-Eighth Supplement to Dana's Mineralogy; by GEO. J. BRUSH, Professor of Metallurgy in Yale College.*

List of Works, etc.

F. X. M. ZIPPE: Lehrbuch der Mineralogie mit naturhistorischer Grundlage. pp. 450, 8vo, mit 334 Fig. Wien, 1860.

A. DESCLOIZEAUX: Sur l'emploi des propriétés optiques biréfringentes pour la détermination des espèces cristallisées. p. 88, 8vo. Extrait des Annales des Mines, tome xiv, 1858.

A. DELESSE: Etudes sur le Métamorphisme. Roches granitiques, pp. 77, 8vo. Extrait des Annales des Mines, tome xii.

CARL F. NAUMANN: Elemente der Mineralogie, fünfte vermehrte und verbesserte Auflage. 8vo, pp. 460, mit 483 Fig. Leipzig, 1859.

N. VON KOKSCHAROW: Materialen zur Mineralogie Russlands, dritter Band, Lieferung 1-3, pp. 128, mit Atlas. St. Petersburg, 1859.-This continuation of Kokscharow's great work, contains monographs of the species garnet, magnetite, anal

* In the absence of Professor Dana I have endeavored to give an abstract of the results of the mineralogical researches, published since the appearance of the seventh Supplement.-G J. B.-New Haven, April 1, 1860.

cime and euclase, together with important additional notes upon beryl, cancrinite, nepheline, phenacite, and apatite.

ADAM: Extrait du Tableau Minéralogique. 8vo, pp. 14. Paris.

J. F. L. HAUSMANN: Ueber die Krystallformen des Cordierites von Bodenmais in Bayern. 4to. pp. 16. Göttingen, 1859.

GUSTAV ROSE: Ueber die heteromorphen Zustande der kohlensauren Kalkerde, zweite Abhandlung, mit drei Kupfertafeln. 4to. pp. 48. Berlin, 1859.

VICTOR VON LANG: Versuch einer Monographie des Bleivitriols. 8vo, pp. 54, mit xxvii Tafeln. Wien, 1859.

D. D. OWEN: First Report of a Geological Reconnaissance of the Northern Counties of Arkansas. Little Rock, 1858.-In this report Dr. Elderhorst has contributed much that is of interest in regard to the ores of zinc, lead and manganese, and presented his facts in a manner that will make them of permanent practical value.

H. KOPP und H. WILL: Jahresbericht über die Fortschritte der Chemie und verwandter Theile anderer Wissenschaften für 1858. Giessen, 1859. pp. 859.-Pages 673 to 812 contain Dr. Kopp's excellent review of the progress of mineralogical science for the year 1858. .

H. C. SORBY: On the Microscopical Structure of Crystals, indicating the Origin of Minerals and Rocks. 8vo, pp. 48, with plates. Quart. Jour. Geol. Soc. Lond., xiv, pp. 458-500.

H. DAUBER: Ermittelung krystallographisher Constanten und des Grades ihrer Zuverlässigkeit. Pogg. Ann., cvii, 267, 343, cviii, 439.

W. H. MILLER: On the employment of the Gnomonic Projection of the Sphere in Crystallography. L., E. and D. Phil. Mag. for July, 1859.

DAUBRÉE: Memoire sur la relation des sources thermales de Plombières avec les filous métalifères, et sur la formation contemporaine des zéolithes. Extrait du Bulletin de la Société Géologique de France, [2], xvi, p. 562-591.

A. KENNGOTT: Uebersicht der Resultate mineralogischer Forschungen im Jahre, 1858. 8vo, pp. 229. Leipzig, 1860.-This is a continuation of Dr. Kenngott's excellent reports, and contains a résumé of the results of mineralogical researches made in 1858. Its completeness, and the careful criticisms by Dr. Kenngott render it a most valuable auxiliary in the study of mineralogy.

F. HESSENBERG: Mineralogische Notizen, No. 8. 4to, pp. 32. Frankfurt, 1860. -This number of Hessenberg's mineralogical notices, contains contributions to the crystallography of the species lievrite, realgar, heavy-spar, calcite, sphene, anatase, erocoisite, and malachite.

Descriptions of Species.*

ALBITE [p. 240, VI].-Analyses of albite, (1.) from Oberhalbstein in Graubunden by Desclabissac (Zeitsch. d. deutschen geolog. Gesell., x, 207). (2.) from Calveras County, California, associated with auriferous pyrites and native gold by F. A. Genth (this Journal, [2], xxvii, 249):

ALLANITE [p. 208, I-VI].-Analyses of orthite (1.) from Arendal by Zettel (Ann. d. Chem. u. Pharm., cxii, 85). (2.) mean of four analyses of orthite from Suontaka in Finland by Mendeljef (Kopp's Jahresbericht, 1858, 703):

Si ΕΙ Fe Mn Ce La, Di Ca Mg K Ña й Ĉ

1. 32.70 17:44 16.26 0.34 3.92

15:41 11.24 0.90 0.51 0.24 2.47 0.28=10171 Y 1.5 9.3

0.7

=100.00

*The paging refers to Dana's Mineralogy, and the Roman numerals, in many places added, to the preceding Supplements.