Obrázky stránek
PDF
ePub

only because the recent death of Tchéby- in the plane and movable with it. Then chev, followed in less than two months by the theorem is that any point B of this. that of Cayley, gives them now a special circle moves in a line OB through 0. In pertinence, but because it is of interest to particular B may be the opposite extremity compare one with what is given on “tram of the diameter through A, and we have motion' in Kempe's How to Draw a

А Straight Line,' and the other with its reproduction by no less a master than Clifford

A2 on pages 149, 150 of his Dynamic, whence

B3

C2 I add figure 2.

“Robert's theorem of 3-bar motion takes the following elegant form: Take a triangle

A3

[merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small]

then the points A,B moving on the lines Ox and OB at right angles to each other, viz.: the general case of a plane moving two points thereof on two fixed lines is reduced to this well-known particular case. And the theorem comes to this, that dividing

[blocks in formation]

C

M

ABC and a point 0 and through O draw
lines parallel to the sides as in the figure, the
3 shaded A's are of course similar to ABC.
Now imagine a linkage composed of the
shaded A's and the bars AA, AA,, BB3,
BB, CC,, CC, pivoted together at A, B, C,
A,,A,, B2, B, C,, C1,0; then, however,
the figure is moved [of course Ag, B, do
not continue in the line AB, etc.], the tri-
angle ABC will remain similar to the shaded tri-
angles, and if in any position of the figure we
fix the points A, B, C, then the point 0 will
be movable in a curve, viz.: we have the
same curve described by O considered as the
vertex of OA, B,, where the two radii are
AA3, BB,—by O considered as the vertex
of OA, C,, etc.—and by O considered as
the vertex of OB, C,, etc.”
CAMBRIDGE, Feb. 22, 1876.

"The porism is very pretty ; it was new to me, though I think it ought not to have been so.

Look at the theorem thus: Imagine a plane, two points thereof, A, C moving in fixed lines Ox, Oy. Describe the circle OAC, which consider as a circle fixed

B

the rod AB at pleasure into two parts AM, MB, and drawing MC at right angles, and a mean proportional, the locus of C is a right line through O, which is of course easily proved.” Yours very sincerely,

A. CAYLEY. CAMBRIDGE, May 5.

GEORGE BRUCE HALSTED. AUSTIN, TEXAS, Feb. 15, 1895.

new

THE PROTOLENUS FAUNA.*

of the genera Orthotheca, Hyolithus and DipTHE above article will be one of especial lotheca. A remarkable mollusc having a interest to students of the early Paleozoic helicoid shell and supposed to be a Hetefaunas, since it describes one of the oldest ropod, enables me to establish a known.

genus. The Crustaceans are chiefly of two From time to time during the last thirty groups, Ostracoda and Trilobita, of which or forty years discoveries of fossils have the former are remarkable for the large been made in the Cambrian rocks of east- number of genera and species, as compared ern Canada. Those of the St. Lawrence with the trilobites; two predominant and valley and northern Newfoundland were by characteristic genera are Hipponicharion and Billings referred to the 'Lower Potsdam, Beyrichona. All the trilobites are of genera but at a later date, together with others peculiar to this fauna, except Elipsocephalus, found in that valley and in southern New- which, although one of the dominating foundland, they have been more specially types, also cccurs in the Paradoxides beds of correlated with the Olenellus Fauna by C. Europe. The most characteristic genus or D. Walcott and others.

trilobites is Protolenus, which is abundantly Other fossils found in the lower part of present in the typical beds. the Cambrian rocks in New Brunswick be- The following are some of the salient low the Paradoxides bed were naturally at characters of the fauna as at present known. first thought to be also of this fauna, but, as All the trilobites have continuous eyelobes. This will be seen by considerations advanced fur- is a decidedly primitive character, and its ther on, it does not now seem possible so to value in this respect is shown by the genus establish the relationship.

Paradoxides of the overlying fauna, which The discoveries in New Brunswick have began with small species having such eyefrom time to time been reported in articles lobes, and culminated in the large forms of published by G. F. Matthew in the Transac- the upper Paradoxides beds in which the tions of the Royal Society of Canada, but eye-lobe was considerably shortened. This such important additions were disclosed shortening of the eyelobe was carried still through the collections made by W. D. further in the Oleni of the Upper Cambrian, Matthew in 1892 and 1893, and by him in dwarfed forms, with a general similarity to conjunction with G. van Ingen for Columbia the Paradoxides, in which the eyelobe is alCollege, New York, in 1894, that a special most on a line with the front of the glaarticle on this, the Protolenus fauna, has bella. been written. From this article the follow- The important family of Ptychoparida is abing abstract has been made of the character sent. This family did not have continuous of the fauna, and the conclusions arrived at eyelobes, for in the young, when this profrom its study.

jecting fold first shows itself, it is short and The fauna consists of Foraminifera, at the lateral margin of the head-shield. Sponges, Molluscs and Crustaceans. All the No trilobite with such an eyelobe has been Foraminifera described are referred to the found in this fauna. The Ptychoparidæ had genera

Orbulina and Globigerina; the about a dozen species in the Olenellus sponges include Protospongia and others. Fauna, and became quite common in that The molluscs are mostly hyalithoid shells with Paradoxides, and continued to abound *Abstract of a paper communicated to the New

throughout the Cambrian period. York Academy of Sciences by G. F. Matthew, of St.

The genus Conocoryphe is absent. This is John, N. B.

specially a type of the Lower Paradoxides beds and under, the name of Conocoryphe Olenellus by two marked features; it is trilineata (Atops trilineatus), is claimed as a more primitive and also more pelagic. characteristic fossil of the Olenellus Zone. The way in which the trilobites are bound

The genus Microdiscus is absent. This trilo- together by the single feature of a continubite is especially characteristic of the Olen- ous eyelobe shows'a unity of origin and a ellus Zone and continued to live with Para- close relationship not found in any other doxides. Here it occurs in the Paradoxides fauna. And yet among these trilobites Zone, but is absent from the Protolenus there are forms which in other respects are Fauna.

parallel to the types which developed in The genus Olenellus is absent. Though the later faunas; thus in Protolenus we have carefully looked for, no example of this have the flat pleura with the diagonal furgenus has been found among the trilobites row of Paradoxides and the deeply grooved, of the Protolenus Fauna, hence, though this geniculate pleura of Ptychoparia, and at the fauna apparently holds the place where we same time the prominent glabella and deep might naturally expect to find Olenellus, that dorsal furrows of Solenopleura. Micmacca, as genus proves to be absent, or at least not at has already been said predicated Zacanall characteristic; and, as so many of its as- thoides of a later fauna, and Protagraulos in sociate genera also are absent, we cannot re- its almost obliterated glabella and flat gard this fauna as the Fauna of Olenellus. cephalic shield closely resembles Agraulos

Of the genera of trilobites that are pres- of the Paradoxides Fauna. ent Micmacca has affinity with Zacanthoides. It is a more pelagic fauna than that of It differs in the course of the posterior ex- Olenellus, for we notice the absence of many terior of the dorsal suture. The relation forms differentiated for shore-conditions. will seem closer if we suppose a movement Trilobites with fixed outer cheeks, like of the eyelobe during the growth of Zacan- Olenellus and Microdiscus are absent; calthoides similar to that which occurred in the careous corals and sponges are rare; thickPtychoparidæ, by which the eyelobe was shelled brachiopods and the Orthidæ are drawn in toward the glabella, while at the wanting, or rare; no Lamellibranch is same time there was a projection of the known, but Foraminifera are quite common posterior extension of the dorsal suture out- in some of the beds. ward toward the general angle. If this The question of the antiquity of this fauna change were shown to have occurred in Za- as compared with that of Olenellus is discanthoides, Micmacca might be looked upon as cussed. The facies of the fauna as above an ancestral form of that genus.

described indicates a greater antiquity, In this fauna there is a very primitive as- but if the two faunas were contemporaneous, semblage of Brachiopods, of forms which it that of Olenellus may have reached these is in many cases difficult to assign to any shores first. known genus. Many are small, some are minute, and the larger species belong to the

VOLCANIC DUST IN TEXAS. Obolidæ and Siphonotretidæ.

SOMETIME since the writer was given, for The Gasteropoda have already been al- examination by the microscope, a sample of luded to ; among these Pelagiella (n. gen.) is a white, fine-grained silicious deposit by remarkable for the peculiar aperture which Prof. R. T. Hill, of the U. S. Geological seems to indicate a free swimming Heter- Survey, who writes as follows concerning it : opod.

"The material which I gave you was collected by This fauna is distinguished from that of an old Texas friend of mine, Mr. S. P. Ford, in December, 1893, who said that at first he supposed it was volcanic material from Knox county, Nechalk, but had since come to the conclusion that it is braska, and from the West Blue River, something else. When I wrote to Mr. Ford that I

Seward county, Nebraska,* and estimated thought it was volcanic glass, probably derived from some of the now extinct vents along the Rocky Moun

that about 90% was vocanic dust, there tain front, he expressed some doubt as to this mode of being also numerous rolled quartz grains. origin, and said :

The description of the material collected This specimen was from a solid hill from thirty to by Professor Hill from Wray (B. & L. R. forty feet high, composed entirely of this stuff. The

R.), on the south side of the Republican point I make is that, on account of its thickness, the crater must have been somewhere very close, and if so,

River, occurs in an interesting article by is it not something heretofore unknown in Texas ? Professor Merrill, “On the Composition of The exact locality is on Duck creek, in Dickens county, Certain Pliocene Sandstones from Montana about 50 miles northwest of the Double Mountain.'

and Idaho.'t (Dickens county is in northwestern Texas, in the

Three figures are given showing the shape Brazos River drainage. -Author.) “This specimen undoubtedly comes from the post

of the particles of volcanic glass found in Cretaceous formations constituting the great Llano

the sandstones. In the material from the Estacado. Perhaps you will remember that in 1886 Devil's Pathway (No. 35893 a ) "there are I collected some similar material from near Wray,

many disc-like bodies on the glass particles, Colorado, and Hecla, Nebraska, which was described

colorless and nearly circular in outline, by Prof. Merrill of the National Museum, in the

but the other figures show angular and American Journal of Science. This Texas material seems very similar to that of the Colorada-Nebraska

fluted forms like those above referred to. locality, both in appearance and in geological position. Merrill gives analyses of three samples of I wish that more was known of the stratigraphy of the volcanic dust from Montana and Idaho, the Texas beds. The Colorado specimens occur in

and concludes that they are of andesitic or what is called the White River Tertiary."

tractytic origin. His analyses include lime An examination by the microscope shows and alkali determinations, and the silica that the white material is volcanic glass, in

contents range from 67.76% to 68.92%. the angular and fluted forms figured by Mer- Merrill also states that some volcanic rill,* as characteristic of volcanic dust from

dust from Krakatoa fell on a ship 885 miles Furnas county, in southern Nebraska. Dil

from the source of volcanic activity, so that ler † also describes and figures similar forms

the existence of a layer of volcanic dust at of glass particles from Norway, Krakatoa, a given point may not indicate the proxTruckee River and Breakhart Hill, the lat

imity of the volcano from which the mater a hill to the north of Boston, Mass.

terial came, but a deposit forty or more feet In the same article he describes volcanic thick would hardly form at a great distance dust from Unalashka, which fell in October, from the source. 1883, and discusses volcanic dusts in gen- The volcanic dust obtained by the writer eral. Professor Diller concludes that “ so far

from a layer in the Neocene Lake beds that as definite observations have been made, they underlie Mohawk Valley, in Plumas county, warrant the general assertion, that with oc

California, likewise resembles in the shape casional exceptions, which can be readily of its particles the dusts figured by Diller explained, volanic dust contains a higher and Merrill. An analysis of this material percentage of silica than the lava to which

by Dr. W. H. Melville showed that it conit belongs."

tained 70.64% of silica, and it was thereProfessor Diller has also described some

* See article by J. E. Todd, SCIENCE, Vol. VII., P. * Proc. U. S. Nat. Mus. 1885, p. 100.

373. † SCIENCE, May 30, 1884.

† Am. Jour. Sci., Vol. XXXII., pp. 199–204.

now

fore presumed to be a rhyolitic glass.* The rodian' linguistic stock (i. e., the Geormaterial obtained by Professor H: 11 closely gian), in connection with the pretended resembles the Mohawk Valley material. Sumerian' of lower Babylonia. It is The Texas occurrence is of unusual interest, likely that they will have to back water,' being in a region where evidences of the that comparisons can really be former existence of volcanoes are rare. made. H. W. TURNER.

CUNEIFORM INSCRIPTIONS. WASHINGTON.

Dr. Hugo WINCKLER, in his ‘History of CURRENT NOTES ON ANTHROPOLOGY (VI.). Babylonia and Assyria,' tells us that the

cuneiform method of writing was in use THE CAUCASIC LINGUISTIC STOCK.

among eight nations speaking entirely difCOL. R. VON ERCKERT, of the Russian

ferent languages. Whether this is quite army, already known for an excellent work

accurate or not, we need not stop to conon the ethnography of the Caucasus, has sider, as there can be no question that it just published an epoch-making volume on

had a much wider distribution than used to the languages of that region (Die Sprachen be supposed. Last year the well-known des Kaukasischen Stammes, Vienna, 1895). French archæologist, M. E. Chantre, unIn this he solves the intricate problem which earthed specimens of it at Pterium and has so long puzzled linguists as to the rela- Cæsarea, in Asia Minor, as far west, perhaps, tionship and place of these tongues. He dem- as such inscriptions have been found in onstrates by satisfactory evidence, structural place. The excavations continued by the and lexicographical, that these numerous University of Pennsylvania at Niffer have languages and dialects, some thirty in num- proved rich in finds of tablets. But the ber (the Ossetic, which is Aryan, being of champion recent discoveries appear to be course excluded), belong to one family, those of M. de Sarzec at Tello. A brief acwhich should be called the • Caucasic.' It

count of his eighth campaign in that rich is divided in three groups, the Georgian, locality appears in the Révue Archaeolothe Circassian and the Lesghian. The gique' of December last, extracted from the stock stands wholly independent, all simi

official report of M. S. Reinach. From it larities to either Ural-Altaic or Indo-Euro

we learn that M. de Sarzec opened a small pean proving accidental or unimportant. mound some hundreds of yards from that Which of the groups is nearest the ancient which he had previously worked, and original tongue he does not pretend to de- chanced upon the very archives of the old cide ; but he offers striking testimony to city themselves. They were inscribed on the persistence of the traits of these lan

tablets and neatly stored in trenches, where guages. The Georgian was written as they had rested undisturbed these thousands early as the ninth century A. D., and he

of years. From these deposits he took out gives a letter composed by a bishop in 918. more than thirty thousand tablets, about five It is quite identical, both in syntax and thousand in perfect condition, another five words, with the current tongue of to-day. thousand very slightly injured, and the

All these facts are the more to the pur- others more or less defaced. This magnipose since so much has been made of late

ficent discovery will have the greatest imyears by Professors Sayce, Hommell and

portance in revealing the history and their followers, of what they call the 'Ala- character of the ancient Babylonian civili

zation. * Bull. Phil. Soc. Washington, Vol. XI., p. 389.

« PředchozíPokračovat »