166 



SCIENCE. 



[Vol. XV. No. 370 



■Surely, we must conclude that it is impossible to imagine how 

 moisture could remain in the air or on the earth's surface, un- 

 less space were filled with aqueous vapor. The earth's surface 

 being practically that of a huge drop of water, and this di'op 

 moving round the sun in a supposed vacuum, how could this 

 moisture be prevented from escaping into space unless space was 

 filled with aqueous vapor? Tlie only thing to prevent such an 

 emergency is the thin veil of an atmosphere ; but this, being it- 

 self all permeable and permeated with aqueous vapor, seems in- 

 deed a very poor protection. 



Laplace's nebular theory of the evolution of the solar system 

 points towards the same fact; for, if aqueous vapor has once 

 been uniformly dispersed throughout the solar space, it follows 

 of necessity that this space could not afterwards have become 

 perfectly exhausted of aqueous vapor : gravitation towards the sun 

 and the planets could not establish such a vacuum. 



If it should be used as an argument against my theory, that we 

 might with just as much right expect to find the other constit- 

 uents of the atmosphere dispersed through space in a rarefied 

 -state, then I would say, as has been pointed out above, that these 

 follow the reverse law of aqueous vapor by being contracted by 

 cold, and that makes all the difference. 



The general conclusion I arrive at is, therefore, that the in- 

 terplanetary space is filled with vapor in an exti-emely rarefied 

 state. The sun and each of the planets is sun-ounded by a vapor 

 -atmosphere of a denser state, the quantity of vapor suiTounding 

 each of these bodies depending upon its size and its surface-tem- 

 perature. The sun will for both reasons have by far the lion's 

 share of such a vapor envelope. This theory seems to agree per- 

 fectly well with the following observed facts : — 



1. The retardation suffered by the comet Encke indicates that 

 this comet, when nearest to the sun (that is, at a distance from 

 the sun about that of Mercury) , passes through a medium of 

 -a certain resistance. 



3. The present condition of the surfaces of the four inner 

 planets varies according to their distances from the sun, or, what 

 is likely to be in proportion thereto, their surface-temperatures. 

 On Mars we find more land than water surface, and a clear sky. 

 The conditions on the eai-th in this respect need not be repeated 

 here. As to Venus and Mercury, they possess an atmosphere of 

 great density ; and, as they are constantly covered by clouds, we 

 have no means of ascertaining the proportion between land and 

 sea surface, but their clouded state seems to indicate that they 

 must be entirely or almost entirely covered by water. These 

 varying conditions seem to indicate that the planets are gradually 

 approaching a state of being dried up, or that their waters and 

 vapor envelope are gradually leaving them ; and the conditions on 

 the moon indicate that this state will have been reached when 

 they have become extinct planets. 



3. The moon being an integral portion of the earth, there can 

 be no doubt but it must once have possessed surface waters and a 

 vapor envelope in proportion to its size. It is now an extinct 

 planet, and its surface is void of watei^s. What has become of 

 this water, unless it has passed into space? 



We have hereby gained a fresh point of view, from which it 

 may be worth our while to reconsider the former, present, and 

 future conditions on the earth. Geologists have come to the 

 conclusion that at the time of the coal period there must have 

 been much less land surface than now, and that the atmosphere 

 must then have been much warmer and moister than it is now. 

 The land may, of course, gradually have emerged from out the 

 seas since then, the quantity of water on the earth remaining 

 constant; but it seems exceedingly more natural to suppose that 

 the earth contained much more water during the coal period than 

 it now contains. When, therefore, we nowadays find ancient 

 sea-beds in the highest of mountain-ridges, we need not feel so 

 sure that these have risen to their present elevated position from 

 under the present level of the sea, as probably the sea-level was 

 formerly quite different from what it is now. 



Mathematicians have at various times attempted to determine 

 the outer limit of the atmosphere by calculating at what distance 

 from the earth there would be equilibrium between the centrip- 

 •etal and the centrifugal forces acting upon the smallest particle 



of air, thereby arriving at results varying from fifty to two hun- 

 dred miles, the diflicult point being how to determine the actual 

 mass and density of the particle of air. Other philosophers have 

 seen the absurdity of imagining the situation of an air-particle in 

 a state of uncertainty as to whether to remain with the earth or 

 go off at a tangent, and therefore have concluded that the atmos- 

 phere is practically unlimited. 



Another series of considerations has led to the conclusion that 

 outside the atmosphere of air, which may be estimated at forty 

 or fifty miles, must exist an atmosphere exceedingly thinner than 

 air. These various theories are brought into perfect agreement, 

 and the absurdities are avoided, by assuming my theory of an 

 outer atmosphere of vapor, which is unlimited. 



It is tmly said that there is nothing new under the sun, and 

 we might therefore expect to find that my definition of the atmos- 

 phere is merely a repetition of what has been said at former 

 times. In his excellently written book, Mr. Scott points out 

 that the old biblical scriptures, particularly the Book of Job, 

 contain many a sound reasoning on the atmosphex-e which holds 

 good to this very day. Not having found the information I 

 wanted in modem works on this subject, I took the hint, and 

 looked up these ancient sayings, until I came to a passage by 

 Moses which made me pause. Perhaps Col. Ingersoll may some 

 day point out some serious mistakes in my argument or in the 

 figures I have produced to support it, but at present it seems 

 rather as if Moses managed to give us a pretty clear definition of 

 the atmosphere when he wrote, "And God said. Let there be a 

 firmament [Hebrew, "expansion"] in the midst of the waters: 

 and let it divide the waters from the waters. And God made 

 the firmament, and divided the waters which were under the 

 firmament from the waters which were above the firmament: 

 and it was so. ' ' 



The coincidence between this observation of Moses and the re- 

 sult I have arrived at may perhaps, in our advanced age, be con- 

 sidered merely as a curiosity ; but, considered as a purely objec- 

 tive and perfectly unbiased view of the matter, it seems to me to 

 afford some further interest. Moses could not argue much on 

 atmospheric subjects, as he had no natural sciences to guide him, 

 but neither could they lead him astray. His knowledge of air 

 was very limited. He did not know that it exerts a pressure of 

 fourteeen pounds per square inch, and that this pressure gi-ew 

 much less when he went on to Mount Sinai to wi-ite the Com- 

 mandments; and neither could he have any knowledge of the 

 existence of invisible vapor. But when he walked about in the 

 desert for forty years under a generally serene blue sky, and on 

 rare occasions saw a cyclone set in, then he would observe this 

 phenomenon exactly as Mr. Scott describes it nowadays: "He 

 saw the thin cirro-clouds overhead gi-adually change into stratus, 

 and these gradually growing further condensed and sink to a 

 lower level, until rain ultimately set in." He saw the clouds 

 and rain being formed on the spot, and could have no suspicion 

 of their being caused by vapors rising out of the dry sand of the 

 desert, and so he wrote faithfully according to what he saw. 

 Although, therefore, no doubt, there are more things between 

 heaven and earth than was dreamt of in the philosophy of Moses, 

 when he tells us that there is a firmament between heaven and 

 earth, dividing the waters from the waters, the time may per- 

 haps not be far distant when we shall all agree with him on that 

 particular point. 



The nomenclature of clouds being a question which of late 

 years has provoked considerable dispute, it seems to me, that, 

 according to my explanation of the general atmospheric arrange- 

 ments, clouds might more properly be grouped according to their 

 cause or origin, rather than entirely according to their appear- 

 ance, which is so varying and deceptive. We find, thus, two 

 distinct groups of clouds; namely, what we may call "evapora- 

 tion clouds" and "condensation clouds." 



Evaporation clouds are cumulus-clouds in shape. They are 

 formed by mixture at the summit of a current of damp air rising 

 from the ground. They are unstable and merely indicate a 

 stage in the upward passage of vapors. They are essentially 

 rainless clouds, and found in the expansion or cushion of unsat- 

 urated air. They have their supply of vapor from below. 



