[CHAPTER XII.]

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[215]Some of the results arising from the sun's being a hollow sphere
[216]Repetition of the effects of condensation on the temperature of the nebula
[217]Ideas called up by the apparently anomalous increase of temperature
[218]How heat is carried from the sun to the earth
[219]The sun supposed to radiate heat only to bodies that can receive and hold it,
  and not to all space. The heat of the sun accumulated in a
  hot box to considerably beyond the boiling point of water
[220]The heat accumulated in this way supposed to be due to a peculiar function of the ether,
  as it is a fact that heat can be radiated from a cold to a hot body
[221]The sun must be gaseous, or rather gasiform, throughout. No matter in it solid
  or even liquid. Divisions and densities of shell
[222]The hollow centre filled with gases, whose mass naturally
  diminishes the mean density of the whole body
[223]The amount of this reduction so far defined. The presence of gases or vapours
  in the hollow a natural result of condensation
[223]The hollow centre filled with gases not incompatible with the sun's being
  a hollow sphere. The temperature at the centre may be anything,
  not depending on any law of gases
[224]Further exposition of hollow-sphere theory put off till after
  further development of the construction of the sun

In the last chapter we have endeavoured to point out how much our knowledge of the interior construction of the earth and moon has been increased, and how many difficulties in the comprehension of their construction are overcome by the fact demonstrated in previous parts of our work that they are hollow bodies; and we now proceed to show some part of what may be learned from studying the sun under the same conception of its being a hollow body. We say part of what may be learned, because the whole seems to us to be so great that it would take much more time and space, not to speak of knowledge, than we can devote to the subject to make even a proper beginning to such a study. To our sight it takes away the necessity for guessing in the dark at what the construction may be, which is all that has hitherto been done; and furnishes the means of discovering, with intelligent study and investigation, what most probably is the actual constitution of the sun.

In Chapters [V]. and [VII]. we have followed up the contraction and condensation of the residue of the original nebula, after it had thrown off all the known planets; first, to the diameter of 58,000,000 miles, with density of 1/274th of an atmosphere and temperature of -273°, or one degree of absolute temperature; second, to about 9,000,000 miles diameter, with density equal to air at atmospheric pressure, and temperature represented by zero of the centigrade scale, or what has been hitherto called 274° of absolute temperature; third, to 4,150,000 miles diameter, with density equal to ten atmospheres and temperature of 2740° of actual, or 2742° of absolute temperature; and fourth, to 972,895 miles diameter, with density equal to water and temperature which we do not venture to express. All these stated densities and temperatures are understood to be average, the temperatures being those the various stages would have had, had no heat been radiated into space by them.

Here, then, we might go on to set forth what might be the interior dimensions, various densities, and conditions of each one of the four stages, under the conception of their being all hollow spheres, and afterwards carry on a résumé of the whole of them and apply it to the sun as it is at the present day; but this, in addition to involving an immense deal of difficult work, subject to errors and omissions in operation, would not do much towards enabling us to explain in a more simple way what may be, most probably is, its interior construction. We shall, therefore, look upon the four stages as represented by a model having the diameter and other known measurements of the sun in its present state.

To begin what we propose to do we believe it is necessary to repeat, as a thing that has to be borne in mind, that when we had contracted the original nebula from 6,000,000,000 miles in diameter to 58,000,000 miles, its density was only equal to a barometric pressure of one-ninth of an inch of mercury, and its mean temperature had been increased only one degree, that is, from -274° to -273°; and we can add that, although we had given the original nebula ten times that diameter, the result both in density and temperature would have been the same when it was condensed to 58,000,000 miles in diameter. Then, again, we believe it necessary to repeat that by contracting the nebula from 58,000,000 to 9,000,000 miles in diameter its mean density was raised from 1/274th to full atmospheric pressure, and its mean temperature from -273° to zero of the ordinary centigrade scale, i.e. to the temperature of freezing water. These two results strike us, at first sight, as somewhat remarkable, seeing that what looks like almost unlimited condensation to 58,000,000 miles diameter produced only one degree of temperature, while the comparatively insignificant condensation of from 58,000,000 to 9,000,000 miles in diameter produced 273° of heat, in the way we are accustomed to measure heat.

Following up these two facts gives rise to ideas that have been borne in upon us ever since we stumbled upon them when making the analysis of the nebular hypothesis. One of these notions was that, were it practicable, the most effectual mode of liquefying gases would be by putting any one of them into a sealed vessel, and confining it in another vessel in which a vacuum of 1/274th part of an atmosphere could be produced; no difficult matter as far as the vacuum is concerned, for a good exhausting air-pump would be all that is required. But the practicability? The vessel in which the vacuum is produced would have to be protected so that no extraneous heat could be conveyed or conducted into it in any way whatever. How this could be, or is, done without cutting off every possibility of manipulating the enclosed vessel, we do not see; but it seems evident that some method is available because something presenting the same difficulties has been actually done, as everybody knows. The only degree of vacuum of any use in the exterior vessel would be about one-ninth of an inch of mercury, because that would as we have just said, furnish a temperature of -273°. There would be no necessity for applying pressure to the gas experimented upon. In fact pressure would be an obstacle to the experiment, according to the theory of the air thermometer; and could only be of use by furnishing a larger quantity of liquid to be handled and examined.

Another idea is that there can be no such condition as absolute zero of temperature of what we are accustomed to think of as a gas, as far as science is concerned; as on arriving at that condition, perhaps long before, any gas would slip out of its hands altogether. But there is a much more rational reason than this, which we have brought forward on a former occasion. We are taught that heat is a mode of motion, which means that as long as there is heat there will be motion to account for it, so that motion would have to be annihilated on the earth before absolute zero of temperature could be reached. We have, then, to come back to what we said when treating of the heat of space, and look upon the temperature of the vibration of the ether as being the lowest that can be measured by science. We said then that it must be far below -225°. Since then a temperature has been reached of within 23° or 24° of absolute zero, according as that condition is measured by 273 or 274.