No\-EMBER 1, 1899.] 



KNOWLEDGE. 



251 



notes and other observations. After measurement here, 

 they will be returned if desired. The value of the results 

 will be much increased if similar photographs can be 

 obtained by a second camera from ten to forty miles 

 distant, and preferably north or south of the other. 



Edwaed C. Pickering. 

 Harvard College Observatory, September 18th, 1899. 



THE "SEAS" OF THE MOON, WHAT 



ARE THEY, AND WHAT IS THE CAUSE OF 



THEIR OBSCURE APPEARANCE? 



By J. G. 0. Tepper. 



THE dark areas in the moon known as " Seas " were 

 originally considered to be real seas, but now that 

 it is known positively than no water can exist 

 there, either as such, or as ice, or vapour, the 

 dark areas still remain unexplained. For, while 

 perfectly visible at the full in distinct outlines of one form, 

 they either disappear entirely in very oblique light, or 

 their form is wholly changed. This shows that the dark 

 appearance is merely the effect of excessive absorption of 

 light, and of diminished reflection according to the inci- 

 dent angle, but not of irregularity of surface, i.e., effect of 

 shadows. 



In venturing to suggest a possible explanation, I do so 

 with the distinct aim of initiating a discussion on the 

 phenomenon, and not of proving the suggested hypothesis 

 as anything more than probable. 



The moon is known, or rather accepted, to be a dead 

 world, (.(>., one once exhibiting similar phenomena of 

 physical life to our own, viz., supporting vegetable and 

 animal organisms. 



Now what would happen if our Earth suffered the same 

 fate •? 



The great bulk of both plants and animals consists of 

 water and carbon. The burning of the latter, its com- 

 bination with oxygen, produces the bodily warmth requisite 

 for animal life, the combination escaping in gaseous form 

 into the atmosphere as carbon dioxide (CO*) popularly 

 known as carbonic acid, which in Nature plants alone can 

 dissociate, and so as to reproduce the carbon in suitable 

 form for food. Besides this, carbon forms the fuel for the 

 production of artificial heat, as wood, coal, kerosene, etc. 



If the water supply is at all small in comparison with 

 anhydrous minerals eager to combine with it into perma- 

 nent heat-resistant compounds (rocks), it will gradually 

 diminish and finally disappear. The same wiU be the case 

 with the nitrogen of the air as well as the oxygen, the 

 greater part of oxygen being locked up for the time in 

 vegetable substances, such as wood, coal, mould, and 

 animal bodies, while nitrogen would principally be 

 absorbed by animals and caustic alkalies together with the 

 remaining oxygen. 



With the diminution of the water, and the atmospheric 

 gases the decay (disintegration) of dying organisms would 

 be at first more and more delayed until all were dead 

 besides the mould of the soil, the last memorials of 

 organic life. 



There being no longer any amelioration of heat or 

 cold through the biophysiological action of plants, air, 

 etc., they would now succeed each other without grada- 

 tion. While the cold would tend to preserve the carbon 

 compounds, the heat, with the sun pouring its rays on 

 the highly absorbent rocks for half a month would 

 probably raise their temperature to, or above, 200° or 

 300° Cent. ; then the organic bodies would be gradually 



dissociated (not burned but charred, for there would not 

 be sufficient oxygen), the excluded gases and moisture 

 would be eagerly appropriated by the nearly red hot 

 minerals, and locked up permanently among the rocks. 



The only substance that would remain unprovided for 

 on account of its weak affinities to any of the common 

 gases at high temperatures would be carbon, and most 

 likely in the form of dust, or minute flakes, wafted by 

 the more and more decreasing currents of the last 

 remnants of an atmosphere to the lee of gentle declivities, 

 and upon the great low-lying plains, wherever the opposing 

 currents counterbalanced each other. 



Since the total disappearance of the atmosphere no 

 currents can possibly exist, and the finest, lightest dust 

 must remain eternally undisturbed, except by the rude 

 shock of a colliding meteor, or when ploughed aside by 

 such, if gliding along after a very oblique impact. 



It is weU known that there is no body more absorptive 

 of light than finely divided carbon particles, hence their 

 intensely black aspect. At the same time, dust, or loosely 

 cohering matter, reflects little light, except at very oblique 

 angles of incidence. 



In the " seas " of the moon we may, therefore, have 

 large areas covered by carbonaceous dust, the last remains 

 and the last evidence of the former vegetable and animal 

 organisms of our satellite. For the one class cannot possibly 

 exist without the other, unless in the lowest forms known 

 as Protozoa and Protophyta {i.e., the same organism 

 discharges the function of both, in absorbing carbon and 

 nitrogen exclusively). 



As an hypothesis the above appears to me to fulfil most, 

 if (perhaps) not all, the conditions demanded in the 

 works perused by me, and I shall be glad to learn wherein 

 it fails. 



Hctttrs. 



[The Kditors do not hold themselves responsible for the opinioLS or 

 statements of correspondents.] 



•MAN; PAST A>'D PRESENT." 



To the Editors of Knowledge. 



Sirs, — In his appreciative notice of this book, for which 

 he has my best thanks, your reviewer objects to my 

 use of the expressions " old stone age " and the "new 

 stone age " as applied to " chronological periods ; more 

 properly they apply to stages of culture. We cannot but 

 think that such abuse of the terms leads to much con- 

 fusion. Wc speak of a neolithic period as if it were a past 

 age. So it is, so far as we are concerned, but it may be 

 pointed out that there are stUl many savage races living in 

 a stage of neolithic culture." This is also my teaching, 

 and I take some pains to make the matter plain in the 

 " Ethnology," which the writer has evidently not seen, but 

 is necessary to the right understanding of " Man ; Past 

 and Present." Thus, p. 72 : " The question is beset with 

 snares and pitfalls, due especially to the fact that the very 

 terminology itself does not everywhere connote the same 

 order of sequence, much less the same periods of absolute 

 time. Thus palfeolithic implements in the New may in 

 some cases correspond with neolithic implements in the 

 Old World, and in all the continents except Australia, 

 where one order alone exists, various phases of progress go 

 on simultaneously rather than consecutively." After giving 

 several instances, I go on (p. 78) : " Such overlapping of 

 old and new, such persistence of low primitive cultures in 

 the midst of highly advanced populations, tend to obscure 

 the time relations, which are here under consideration. 

 It is obvious, for instance, that implements of the most 



