444 



NATURE 



{Sept. 1 6, 1875 



of Dartmouth, at the base of the chromosphere, though the 

 chromospheric shadow should perhaps be taken into^the account. 

 The importance of a .-ui.y of this absorbent atmosphere be- 

 comes evident if we admit that the greater part of the 500° 

 which separate the temperature of t'le temperate zone from abso- 

 lute zero is principally due to the sun's radiation. To this 

 atmosphere new matter is constantly being added and taken 

 away by the continual changes of the interior surface. Any 

 alteration in the capacity for absorption— say a difference of 25 

 per cent., which could hardly be recognised by observation — 

 would alter the temperature of our globe by 100°. The e xist- 

 ence of life on the earth is clearly dependent on the constancy 

 of the depth and absorption of this solar envelope. Hitherto 

 we have chiefly confined calculations to the diminution of solar 

 heat by contraction of the sun's mass — an operation likely to go 

 on with great uniformity. But here is an element of far more 

 rapid variation. If changes in the depth of this solar envelope 

 are cyclical, they would be accompanied by cyclical alterations 

 of earth's temperature. This may serve alike to explain the 

 characteristics of variable stars and the vast secular changes on 

 earth indicated by geology. If the law of alterations in that en- 

 velope can be ascertained, new light may be shed on the history 

 of the globe and the near future of life upon it. 



Prof. Thomas Meehan, of Germantown, Penn., made an attack 

 on Darwinian theories in a paper which disputed the assumption 

 that insects are a material aid in the fertilisation of plants. He 

 drew the following conclusions: (i) That the great bulk of 

 coloured flowering plants are self-fertilisers. (2) That only to a 

 limited extent do insects aid fertilisation. (3) Self-fertilisers are 

 in every way as healthy and vigorous, and are immensely more 

 productive, than those dependent on insect aid. (4) That when 

 plants are so dependent they are the worse fitted to engage 

 in the struggle for life — the great underlying principle in natural 

 selection. 



Prof. Morse described the evident characteristics of insects 

 which seemed not only fitted for fertilisation, but were found 

 actually engaged in the process. He was not prepared to aban- 

 don the vast mass of facts already obtained on account of the 

 few and doubtful experiments detailed by Prof. Meehan. Prof. 

 Riley thought that the fact that insects were absolutely essential 

 to the existence and perpetuation of many plants, had been proved 

 by experiments and observations so numerous and convincing 

 that it could no longer be denied. He mentioned his own ex- 

 periments with the Yucca ; and he met and combated the theory 

 that self-fertilisation, like interbreeding, did not tend to deterio- 

 ration. Prof. Meehan, in explanation of his views, stated that 

 he regarded the present dependence of plants upon insects as an 

 evidence of weakness and accident, or of deformation in the 

 plant. Prof. Riley said that it was a mistake to suppose that 

 insect life was scarce in the Rocky Mountains. 



A paper was presented On some New Fossil Fishes and their 

 Zoological Relations, by Prof. J. S. Newberry, of Columbia 

 College, giving brief descriptions of interesting fish remains 

 found during the past year in the Devonian and Carboniferous 

 rocks of Ohio. Of these, the most important "find" was that 

 of nearly the entire bony structure of a single individual of 

 Dmichthys Terrellii, the hugest of all the old armour-plated 

 Ganoids, Life-size drawings of most of these bones were exhibi- 

 ted to the Association, and copies of them will appear in the 

 second volume of the "Geology of Ohio," now going through 

 the press. Drawings of another species of Dmichthys was 

 shown {D. Hertzeri) in which the maxillaries and mandibles 

 are set with teeth instead of being sharp-edged. The remains 

 of both these monsters have been found only in the upper 

 Devonian rocks of Ohio. Prof. Newberry also exhibited to the 

 Association teeth of Dipterus Glenodus, and those of a new 

 genus belonging to the same family. 



Prof. E. D. Cope, of Philadelphia, made a communication 

 On the indications of Descent exhibited by North American 

 Tertiary Mammalia. The gradual development from one 

 form to another| by changes in the foot bones was traced 

 through a long series from extinct Tertiary animals to those of 

 the present day. A similar process of change was traced in the 

 teeth of animals, the simpler forms of te-ith in the Eocene 

 being a crown with four tubercles. The human skeleton. Prof. 

 Cope declared, Iretaiaed many more ancient types than other 

 Mammalia. 



A paper from Prof. Daniel Kirk wood, of Bloomington, Ind., 



On the Distribution of the Asteroids, was read by Prof. Langley. 



Prof. Kirkwood stated that twenty years ago, when the number 



. of known asteroids did not exceed fifty, it was inferred from 



purely physical considerations that there must be great irregu- 

 larity in their distribution, and that gaps would be found in their 

 zone where their periods were commensurable with those of the 

 planet Jupiter. In 1866, when the number of asteroids amounted 

 to eighty-eight, the agreement of theory and observation in this 

 matter was the subject of a paper from Prof. Kirkwood, read at 

 the Buffalo meeting of the Association, and the evidence was 

 again summed up in a paper at Indianopolis in 1871. Since 

 then thirty-one asteroids have been added to the group. It is 

 now proposed to show that the truth of the theory advanced in 

 1866 is now more than ever determined. The Professor pro- 

 ceeds to divide the space between the asteroids into six zones by 

 orbits whose periods would be commensurate with those of 

 Jupiter. Then taking the members of the group in the order of 

 their mean distances, it is found that the widest intervals between 

 them are at these gaps where orbits would coincide with certain 

 multiples of Jupiter's revolution. He remarks that it is a notable 

 fact in the development of the solar system that the largest 

 planet, Jupiter, should be succeeded by a space so nearly desti- 

 tute of matter as the zone of the asteroids, the ratio of masses 

 being as i to 5180. An explanation of the disproportion 

 was given in a paper read in 1870 ; but it may be asked 

 what might have been the result if the density of the asteroidal 

 group had been equal to that of the other planetary rings. For 

 reasons which he assigns, Prof. Kirkwood believes that if the 

 asteroidal group had possessed a total density half that of Jupiter, 

 they would when nebulous have been brought so closely into 

 contact by the great planet's attraction as to fuse into one, 

 instead of remaining as separate bodies. A similar result he 

 regards as having taken place in the case of Uranus. A forma- 

 tion of the same kind would result where the period of a planet 

 was one-third that of Jupiter ; corresponding to the ratio 

 between the periods of Jupiter and Saturn. The rare instances 

 of great inclination among asteroids' orbits he is inclined to 

 believe may have been occasioned by comets, when the minor 

 planets were themselves in a cometary or nebulous condition. 



The Hon. L. H. Morgan, of Rochester, read papers On 

 Ethnical Periods and the Arts of Subsistence. The discussion of 

 ethnology would be much facilitated by the use of a certain 

 number of ethnical periods representing conditions in the advance 

 of man from his earliest to his higher conditions. Mr. Morgan 

 proposes the following : — 



1. A period of savagery. 



2. The opening period or lower status of barbarism. 



3. The middle period of barbarism. 



4. The closing or upper period of barbarism, 



5. The period of civilisation. 



The ages of stone, bronze, and iron have served a useful pur- 

 pose in archaeology, but the progress of knowledge has rendered 

 more definite subdivisions necessary. The use of stone imple- 

 ments began far back in savagery, which extended even to the 

 introduction of tools of iron. The successive arts of subsistence 

 offer distinctions of more value. The period of savagery begins 

 with the human race. The invention or practice of the art of 

 pottery may enable us to draw the line between savagery and 

 barbarism. 



The transition from the lower to the middle stages of bar- 

 barism is marked in the eastern hemisphere by the domestication 

 of animals ; in the western by the cultivation of maize and suc- 

 culent plants by irrigation, together with the use of adobe and 

 stone in house architecture. The upper status of barbarism is 

 cut off from civilisation by the invention and use in the latter ot 

 a phonetic alphabet and the art of writing. 



In respect to the effect of arts of subsistence in modifying the 

 improvement of mankind, Mr. Morgan takes very broad views. 

 He is of the opinion that success in multiplying the sources and 

 amount of food decided the question of man's supremacy on 

 earth. His advance has been identified with improvement in 

 this particular. 



Prof, Burt G. Wilder, of Cornell University, read papers on 

 the following natural history subjects : — Notes on the American 

 Ganoids {Amia, Lepidosteus, Acipenser, and Polyodon) ; The 

 Use and Morphological Significance of the Caudal Filament of 

 the young Lepidosteus ; The Embryology of Bats ; The Affinities 

 and Ancestry of the existing Sirenia. This paper was based 

 upon three specimens which were exhibited. First, a foetal 

 Dugong, 24 feet long, obtained from Australia through Prof. H. 

 A. Ward. Second, a fretal Manatee, between three and four 

 inches long (as if extended), obtained from South America 

 through Prof. James Orton. Third, a foetal Cetacean (probably 



