444 



NATURE 



[Oct. I, 1874 



tance ol one-and-a-half miles, while a 2500-pound bell would 

 not set the same sand in motion at a distance of thirty yards. 



It has been frequently observed that a distinct echo is some- 

 times obtained from the ocean. Prof. Tyndall tliinks llie reflec- 

 tion is from surfaces of wind. Prof. Henry thinks it is from the 

 surface of the waves of the ocean, and that the sound is after- 

 wards refracted by the w ind. 



In a paper On the Tails of Comets, Mr. Henry M. Parkhurst 

 endeavours to give data for predicting the form and appearance 

 of these appendages. 



Thenno-electrie Properties of Minerals, by Professors A. 

 Schrauf and E. S. Dana. — The interesting investigations of the 

 late Gustave Rose, an eminent mineralogist at Berlin, have, 

 during two or three years past, excited considerable interest in 

 this subject. He began with the fact first announced by Ilankel 

 that some crystals of pyrite and cobaltite are electrically positive 

 and others negative, and the endeavour to explain this opposite 

 character on the assumption that it was connected with a condi- 

 tion of the right and left hemihedrism cliaracteristic of both 

 species. This touches a fundamental point in molecular physics, 

 and if it could be sustained, Rose's hypothesis would, be very 

 valuable. 



Schrauf and Dana, however, after the examination of a large 

 number of minerals, comprising nearly all the metallic sulphids, 

 have come to the conclusion that the cause of the variation of 

 electrical character in this species must be sought elsewhere. 

 They attribute it not to an opposite molecular condition shown 

 in the hemihedral crystals, but to a change in chemical composi- 

 tion. They call tlieir attention, in the lirst place, to the series of 

 Seebach, where, for example, platinum occupies a vaiying posi- 

 tion accoi'ding to its degree of purity ; moreover, they urge that 

 the single case observetl by Stefan, where some specimens of 

 granular galena are positive and others of crystallised galena 

 negative, is strong evidence against the inlluence of hemihedrism, 

 as nothing of the kind can be assumed here. The force of their 

 argument lies in the fact that they have found several other well- 

 defined cases ol minerals having peculiar varieties, and that 

 among minerals crystallising holohedrally. Chemical analyses 

 were here desirable to show how far the material under investiga- 

 tion varied in composition. In the absence of these, however, 

 the specific gravity was resorted to as an indicator of the chemi- 

 cal character. 



This afforded decisive results of plus and minus varieties of 

 species, showing a decided difference in density and implying a 

 corresponding change in composition. This was true also, in a 

 marked manner, of ciibaltite, and in a somewat less degree of 

 pyrile, showing in each case where the explanation for the elec- 

 trical character was to be looked for. 



Several other conclusions were deduced from the long list of 

 observations contained in the paper, but the foregoing will be 

 sufficient to indicate its principal points. 



Distribution of American WooJlamls, by Prof. Wm. II. 

 Brewer, of New Haven. — The flora of the United States, the 

 author said, is believed to contain over 800 woody species, and 

 oyer 300 trees. Of these trees, about 250 species are somewhere 

 tolerably abundant, about 120 species grow to a tolerably large 

 size, 20 attain the height of 100 ft., 12 a height sometimes of 

 over 200 ft., and a few — perhaps 5 or 6 — a height of 300 ft. 



Notes on Tree Gro-H'th, by Prof. Asa Gray, of Cambridge, 

 Mass. — Whether the trunk of a tree increases in length, in the 

 parts once formed, is still an open question in the popular mind. 

 From careful observations ni.ade by Prof. Gray and many others, 

 the conclusion is that the trunks of trees do not grow in length. 



Natural History at I'emkese, by Prof. F. W. Putnam.— In 

 speaking of the method of teachmg at Penikese School, Prof. 

 Putnam said :— " Text-books are not allowed. Our way was to 

 give e ch student a specimen of fish and ask him or her to study 

 that lish and tell llie instructor what had been observed. Thus we 

 developed their powers of observation upon the external character 

 of the fish. After they had studied the fishes for about two days, 

 they were called upon to state what they had seen. Then the 

 anatomy of the specimens was gone into, and the students were 

 led on stop by step until they had secured a very firmly founded 

 idea of the structure of a vertebrate animal. 'I'hen we asked 

 questions as to the character of vertebrates, and finally they began 

 to be original investigators. We really demonstrated in a praci ical 

 way the subject, which is exciting so much attention now, of co- 

 education of the sexes. We found that the ladies of the school 

 were as capable in every way of making careful dissections and 

 rendering careful accoun's of the work they had done as the 

 gentlemen, and, in fact, f.ur or five '.f llie ladies became original 



investigators before any of the gentlemen. This showed con- 

 clusively that the ladies had the power of becoming original 

 investigators in science if they only would give the application." 



Organic Change proJuced in the Bee, by Sophie B. Ilerrick, of 

 Baltimore.— This was a very interesting paper, containing the 

 authoress's own observations and experiments on bees. 



The Kez'ersion of Thoroughbred Animals, by Prof. Wm. H. 

 Brewer. — It is often claimed that if the care of man be with- 

 drawn an improved breed will retrace the steps of its ancestry 

 and revert to its original characteristics. For some years Prof. 

 Brewer has been investigating this subject and seeking for proof 

 of the alleged tendency to reversion. To carefully-worded in- 

 quiries in writing, following upon every report of such '* rever- 

 sion," Prof. Brewer has received very numerous replies, and thoy 

 are unanimously in the negative. This is certainly remarkable, 

 following upon the confident assertions that animals so frei|uently 

 exhibited the alleged tendency. The inquiries were pushed in the 

 specific localities where the reversion was said to have occurred ; 

 the questions have been put to a large number of stock-breeders, 

 and finally have been made by means of a printed circular. But 

 the result was always the same, except that a smile of incre- 

 dulity extended over the faces of some stock-breeders when such 

 inquiries were put to them, and they feared they were to be 

 made the victims of a "sell." No instances of the alleged 

 " reversion " having been authenticated in Prof. Brewer's expe- 

 rience, he asked the Association to aid in exposing and refuting 

 the pernicious notion. 



REPORT OF PROF. PARKER'S HUNTERIAN 

 LECTURES "ON THE STRUCTURE AND 

 DEVELOPMENT OF THE VERTEBRATE 

 SKULL"* 



Yll.— Skull 0/ lite Snake (Coluber natrix). 

 A MONG the most noticeable features of the Ophidian 

 -^~^ skull may be mer^tioned the ivory-like texture of the 

 bones, the immense strength and compactness of tlie 

 brain- case, and the equa'ly remarkable mobility of the 

 facial bones, the maxillary and palatine apparatuses and 

 the lowerjaw being arranged in such a way as to allow of 

 the greatest possible extension of the mouth during de- 

 glutition. Another important characteristic is the bony 

 completeness of the brain-case, which is as thoroughly 

 closed in as that of a mammal, scarcely any part of its 

 walls being formed in the adult either by cartilage or 

 fibrous tissue ; the inter-orbital septum, also, or laterally 

 compressed anterior moiety of the basis cranii, so charac- 

 teristic of the Sauropsida, is absent, the base of the skull 

 being flat throughout, and abruptly terminated in front. 

 But the most interesting and at the same time most 

 anomalous feature is the persistence of the fcetal trabecular, 

 in the form of two slender cartilaginous rods (Fig. 23, Tr), 

 lying in grooves on either side of the parasphenoid. 



The hmder part of the skull is formed by a well-ossified 

 occipital segment, the four elements of which are firmly 

 united with one another by suture ; the single convex 

 occipital condyle is borne chiefly by the basi-occipital, the 

 exoccipital, however, taking a considerable share in its 

 formation. The basi-occipital is continued forward by a 

 broad, expanded, basi-sphenoid, produced anteriorly into 

 a slender prolongation or rostrum (Fig. 22, Pa.S), which 

 underlies the front half of the brain-case, and answers to 

 the parasphenoid bone. 



The parietals are completely fused together in the mid- 

 line, where they are produced in the Pythons and Boas into 

 a strong sagittal crest for the attachment of the temporal 

 muscles. In theirhinder half they are simply roofing bones, 

 as in Lizards and Amphibia ; but in front of the auditory 

 capsule they extend downwards (Fig. 23, I'a') and meet 

 the parasphenoid, forming with it a complete cylindrical 

 cavity. The frontals, unlike the parieiils, have only a 

 sutural union with one another ; but they, tou, are produced 

 downwards (Fi'), and, moreover, come into contact with 

 one another below, above the parasphenoid, so as to form 



' Coiilinued from p iy'. 



