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"But this small gravitative power of the moon would prevent its retaining on its surface any of the gases forming our atmosphere, which would all escape from it and probably be recaptured by the earth. By no process of external aggregation of solid matter to such a relatively small amount as that forming the moon, even if the aggregation was so violent as to produce heat enough to cause liquefaction, could any such long-continued volcanic action arise by gradual cooling, in the absence of internal gases. There might be fissures, and even some outflows of molten rock; but without imprisoned gases, and especially without water and water-vapour producing explosive outbursts, could any such amount of scoriae and ashes be produced as were necessary for the building up of the vast volcanic cones, craters, and craterlets we see upon the moon's surface." From Is Mars Habitable? by ALFRED RUSSEL WALLACE F.R.S., ETC.

I am not a science expert at all, so I don't think myself fully understand the content of the excerpt above. But I cannot bring myself out of doubt that the highlighted part is positive sentence, considering the preceding sentence which is in negation. So the cluase in the highlighted part should be also negative, I guess. What I mean is not based on syntax, but semantics. What I undertand as follows: Volcanic activity cannot occur without internal gases(imprisoned gases), and no matter how powerful external aggregation is, it cannot make volcanoes on the moon. Please help me.

  • It's pretty horrible writing. I could probably try to understand it completely, but I really don't want to. There has to have been a far better way to express this point. Is the writer a non-native English speaker? – Andrew Nov 13 '18 at 1:46
  • en.wikisource.org/wiki/Author:Alfred_Russel_Wallace He is a british naturalist, it says. – NAM Nov 13 '18 at 2:01
  • Yeah, well, unfortunately in English as in any language, there are plenty of native speakers who refuse to use two words when twenty will do. – Andrew Nov 13 '18 at 4:01
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Think of something with a soft cushion, like a pillow or bed. The softness comes from air inside that gets compressed. Tables and beds are pretty similar -- the biggest difference is the soft mattress on the bed. Put something heavy on a weak table and the table will just crack (like a fissure) and break. But put something heavy on a bed, and the mattress will "crater" before the frame breaks.

Also, think about toilet paper: the cheap stuff you might find in a public toilet versus the quilted 2-ply or 3-ply you might buy yourself. The quilted TP is "squeezably soft" because of all the air trapped inside, but the cheap TP is usually pretty hard because of how much paper the manufacturer tries to include.

There might be fissures, and even some outflows of molten rock; but without imprisoned gases, and especially without water and water-vapour producing explosive outbursts, could any such amount of scoriae and ashes be produced as were necessary for the building up of the vast volcanic cones, craters, and craterlets we see upon the moon's surface.

The author is stating that although there is evidence of volcanic activity, there's not the right kind of volcanic activity. Without the explosive force of trapped gases, and an atmosphere for dust and ash to both mix with and be moved by, the ground of Mars will not be conducive to the creation of Moon-like terrain.

  • Thank you for the reply, and as you mentioned, the ground of Mars(actually I didn't catch the author is talking about Mars) will not be suitable for creating volcanic terrain because of the lack of gases. But in the bolded sentence above, the main clause(could any such amount of scoriae and ashes be produced as were necessary for the building up of the vast volcanic cones, craters, and craterlets we see upon the moon's surface) does not have any negation element. That is the point where I am lost. Semantically, the cluase should be in negation, but it is positive sentence. – NAM Nov 13 '18 at 5:06
  • I just noticed something myself: Is there a word missing or is the ending punctuation supposed to be a question mark? The second half the sentence (but without...moon's surface) is phrased as an interrogative. Or is 'any' supposed to be 'no'? – miltonaut Nov 13 '18 at 23:27
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    I googled and searched the original book. The punctuation is a period, not a question mark, which means the clause is not in the form of interrogative. No missing word. Any was used not No. This clause is really killing me. I guess it is subject and verb inversion. – NAM Nov 19 '18 at 2:52
  • I agree with the bad writing sentiment. It would be much clearer if the author phrased it as "...but without imprisoned gases, and especially without water and water-vapour producing explosive outbursts, any such amount of scoriae and ashes could not be produced as were necessary for the building up of the vast volcanic cones, craters, and craterlets we see upon the moon's surface." – miltonaut Nov 19 '18 at 14:43

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