236 FROM NEBULA TO NEBULA 



liquid air. Let us compare that density with the density 

 of Doctor See's nebula. Taking the minimum radius 

 mentioned by him, namely, a trillion miles, and dividing 

 by the radius of Neptune's orbit, 2,800,000,000, gives the 

 number 350, which being cubed reveals that See's nebula 

 is, in round numbers, 43,000,000 times as rare as La- 

 place 's ! We can get a more concrete idea of its extreme 

 tenuity by multiplying the side 535 feet by 350 and erect- 

 ing about this distance, as one edge, a larger cube, 35 

 miles each way. Such a cube would cover with its base 

 the entire area of the State of Rhode Island, land and 

 water. The air from such a cube, supposing it through- 

 out of the density at sea level, if reduced to liquid form, 

 would fill a cubical vat four miles each way (64 cubic 

 miles). Discard this all, retaining but a single cubic inch 

 of it, as in our former illustration, and restore it to the 

 great void of 42,875 cubic miles out of which it came, and 

 you acquire a mathematically accurate idea of the sort of 

 nebula Doctor See is dogmatizing about. However, one 

 distinction it is important to note, namely, that in place 

 of using the substance air, which is a gas, we should sub- 

 stitute, say, a heaping teaspoonful of fine flour. Such, 

 then, is the, by courtesy, " density" of the so-called "re- 

 sisting medium" which Doctor See so trustfully adopts 

 as the corner stone for his cosmogonical edifice, or shall 

 we say, as the barrier on which he relies for turning back 

 the charging planets and training them to course in 

 rounded paths. 



But Doctor See has been guilty of even a worse 

 solecism: he has incautiously fallen into the selfsame 

 blunder for which he (rightfully) criticises Laplace, and 

 which, according to his explicit declarations, is the chief, 

 if indeed it be not the sole aim, inspiration and justifica- 

 tion for his own cyclopedically elaborated theory. La- 

 place's conception, he informs us, was fatally defective 

 "because it violated the law of areas" (Kepler's second 

 law), namely, that the radii vector es pass over equal 

 areas in equal times. Let us see, now, if Doctor See's 

 does not commit the same offense. 



