Essays and addresses / by professors and lectures of the Owens College, Manchester.

Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: Essays and addresses / by professors and lectures of the Owens College, Manchester. Source: Wellcome Collection.

    106/584 page 85
    т.] SOLAR PHYSICS. 85 mena of the sun's surface are so extremely violent it is very easy to answer the question. We have only to turn to Art. 17, which tells us the conditions deter¬ mining the intensity of convection currents, and we find that the solar currents are violent—■ Firstly^ because the heat of the hot solar surface is very great as compared with the cold space beyond. Secondly, because the force of solar gravity is very great, being about 28 times greater than that on the surface of our earth. Thirdly, because the scale of the whole arrange¬ ment is very great ; and Lastly, because we have the presence of conden¬ sable substances in the solar atmosphere. All these are powerful causes, and their joint result is to swell the violence of solar storms into something like 00 or 100 miles ^er second. 31. Now, this meteorological activity of the sun's surface is very intimately connected with his light- giving energy. It has often been a source of wonder how the sun can incessantly—without weariness and without abatement—continue to give out such enor¬ mous floods of light and heat, as we know he does. Of course the machinery for such a continuous efful¬ gence must be very powerful. Now what is this machinery ? We reply it is by means of the convection currents of the sun that all this takes place. We can easily see that if the surface of the sun were that of an incandescent solid it would very soon grow cold. Were it a continuous liquid surface there might be convection currents, but these would not be powerful, inasmuch as liquids do not expand through heat nearly
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