HARDWICKE'S SCIENCE-GOSSIP. 



247 



proved connection of comets with streams of me- 

 teors points to a greater mass for the former. The 

 number of components of a meteor-swarm is with- 

 out question very great, and each individual mem- 

 ber of the group has a sensible weight, so that the 

 total mass becomes much greater than that gene- 

 rally assumed for the comet itself. Now whether 

 we consider the comet to be an aggregation of 

 meteors, or a single meteor very much larger than 

 the rest, it would seem certain that it cannot be so 

 despicable a body as has generally been believed. 



In order to collect all the available information 

 before I venture to suggest what may be the peculiar 

 function of comets, I must refer to their chemical 

 constitution as indicated by spectroscopic observa- 

 tion. Three, if not four, comets, including the 

 bright comet of the present year (Coggia's), have 

 been found to yield spectra identical with that of 

 the electric spark when taken in olefiant gas, and 

 the conclusion we must draw is, that carbon in some 

 form or other is the principal constituent of those 

 comets. Several others have yielded a character, 

 istic spectrum differing from this, and which has not 

 been identified with that of any terrestrial sub- 

 stance. We may not say that this will prove a new 

 elementary body, for greater knowledge of the 

 variety of spectra obtainable from terrestrial sub- 

 stances under different circumstances is needed 

 before making such an assertion, and it is more 

 likely that eventually it will be identified with some 

 known element. Erom the simplicity of the spec- 

 trum, and its general resemblance to that of the 

 carbon comets, we are perhaps entitled to assume 

 that they consist mainly of a single elementary 

 substance of somewhat analogous character. 



Other comets may possibly be similar to the 

 meteors, their attendants, which have again and 

 again been analyzed. In them, iron in great quan- 

 tity, nickel, cobalt, silicon, and a variety of other 

 substances, chiefly metals, have been found. Now, 

 all these substances are in strong contrast to those 

 which have beeu identified in those voluminous 

 bodies, the nebulae. Two of the three bright lines 

 which ordinarily constitute their spectra, have been 

 shown to be due to the presence of nitrogen and 

 hydrogen, both gases incapable as yet of being 

 liquefied ; to which class of bodies the third also 

 doubtless belongs. If we imagine all space to be 

 occupied by roving comets, and the enormous if 

 not infinite distances to which they recede from the 

 sun favours such a supposition, it is certain that 

 more or less often they must come into contact 

 with some portion of the extended contour of the 

 nebula, and be retained for ever in the matter 

 thereof by chemical union with its substance. In 

 the course of ages a very large number of comets 

 of various composition would become part and 

 parcel of the nebulous matter, which v/ould more 

 and more tend to the liquid, and upon cooling to 



the solid form, a number whose total mass with 

 accompanying meteor streams would be comparable 

 with that of the nebula itself. Thus the theory 

 to which we are conducted, and which must be • 

 boldly enunciated, is that nebulse are, as has so 

 often been asserted, worlds in course of formation, 

 and that comets are the active agents in producing 

 tbis result, a theory which it seems at present 

 hopeless to establish, but which the generally 

 received doctrines of evolution may induce us by 

 analogy to view with favour. It is worthy of con- 

 sideration that, with one important exception, 

 oxygen,* the substances which would exist in a 

 nebula after the impact of a number of comets, are 

 precisely those which are the principal constituents 

 of an organic world ; but it would be idle to specu- 

 late upon the actual result of the union of comet 

 with nebula until spectroscopic science shall have 

 informed us what are the two other substances that 

 we find so plentifully in the heavenly bodies, 

 namely, the third constituent of the nebulae, and 

 the so frequent component of comets. As the 

 nebulous matter became more and more dense, its 

 gravitational attraction would increase, and the 

 number of comets drawn into its toils would for 

 some time increase also, but as the system became 

 developed, and the central mass assumed the liquid 

 form, they would be enabled to escape after having 

 described their orbits around the newly formed sun, 

 leaving only the lesser and outlying meteorites to 

 swell its mass and maintain its heat, precisely as 

 happens, in all probability, in our own system. 

 Orwell Park Observatory. 



{To he contiriv.ed.) 



ONLY A SPARROW. 



fTlHREE years since last June, an unfortunate 

 -^ sparrow fell at my feet from the roof of a 

 house as I was passing. The miserable little 

 creature was quite unfledged, and somewhat bruised. 

 by its rude contact with the "bare flint stones." 

 Taking compassion, therefore, on this "waif and 

 stray " of misfortune, I carried it to my house, and 

 there confided it to the care of one of my servants 

 With motherly forethought, she swathed the bant- 

 ling in cotton wool and flannel, and for safety, con- 

 signed it to a cage. Every now and then she took 

 the helpless orphan out, and administered to it a 

 "judicious quantity " of sopped bread from her own 

 mouth. The bantling took to its foster-mother and 

 to its diet kindly, and by slow degrees acquired the 



* The unidentifled line in the nebula spectrum is very near 

 an important line in the spectrum of oxygen, but the coinci- 

 dence is not exact, as in the cases of the hydrogen and nitrogen 

 lines, nor have experiments been made upon the last lijie to 

 disappear in the oxygen spectrum when the source of light is 

 made gradually fainter, as in the case of the other two gases. 



