,464 Pluvial Period due to Suit's Influence. 



FIG. 32. 



Sum\ 



A.TYLOR'S ESTIMATE~llY NEWTONIAN LAW. 



N. Jfackas. 

 'i\\, Diameter 74.9 OO -Smiles. Sp;GrS-l 



periodical character. That is to say, the Earth must have received much less 

 sunshine in winter and much more in summer. I calculate that the specific 

 gravity of the sun is not more than o - oo4, instead of 0*2543 as usually stated. 

 If the nucleus of the density of the earth is 5 "], and if this nucleus is one-tenth 

 of the whole diameter, then the density of the gaseous envelope of the sun would 

 be only o'oooi, or about that of hydrogen gas. The weight of the sun seems to 

 be enormously exaggerated. I do not find any careful calculation by any writer ; 

 and I only work it out as one-sixtieth of the weight that has been attributed 

 to it. Chemical changes in the sun's envelope might produce great alteration 

 in the sun's temperature. There is no reason to suppose the heat of the sun 

 should be constant for any long geological period. 



Also the series of rocks commencing with the Silurian, show evidence in 

 every successive period of difference of conditions of life, and this evidence 

 points to constant change in the quantity of heat and light emitted by the sun, 

 and great alteration of atmospheric conditions. 



Particular instances are the abundance of carbonic acid gas in the air during 

 the carboniferous period, and again in the quaternary period. This is shown 

 by Mr. Prestwich's paper,* investigating the cause of the eroded surface of the 

 chalk, and is in one case proved by the rapid formation of coal, and in the 

 other by the occurrence of deep pipes in the chalk, which appear to have been 

 excavated by water containing a large quantity of carbonic acid gas. 



The models and diagrams, however carefully executed, convey a very poor 

 idea of real geological phenomena. Lectures are of very little use, except 

 supplemented by observation in the field. The model of the form of the surface 

 in the chalk at Brading gives an idea of the excavation of the gorge in the chalk 



* Prestwich's Quart. Jour., p. 64, 1855. 



