Penny Blood: Serial Sensation and Working-Class Entertainment — page 79: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

62 ELEVATIONS ON THE [on. v1. adopt some modification of his views as to the condition of the globe at the time at which a rigid crust commenced ‘to form, because we shall find that they lead us to a value of 2ke which is not in accordance with natural appearances. The point which is material in the application of his inves- tigation is, that cooling is to take place by conduction and not by convection. V is the melting temperature of rock; which Sir William Thomson places provisionally at 7000° F., a very high esti- mate. Mr Mallet has shown that the temperature of slag run from an iron furnace is less than 4000° F.* 6b is a temperature such that, , V 7000° 4g 088622 The quantity a is thus defined: a=2,/«t, where « is the conductivity of rock, found by Sir Wm: Thomson to be “ 400 for unit of length a British foot and unit of time a year.” And ¢ is the number of years since the earth became solid, which must have elapsed in order that the rate of increase of tem- perature in descending into the earth should be what it is observed to be. Consequently ¢ is 100,000,000 years, and a =80 miles, We learn (§ p. of Sir Wm. Thomson's paper), that h pe aw NP=- |e a dan. aJQ b = 7900° F. ‘When then the rigid crust was commencing to form, the whole globe, or at any rate its outer portion to a considerable depth, was at the melting temperature V° F. represented on the diagram by Og or Nn. At a subsequent time the tempera- ture at the depth OWN or x was v’, represented by the ordinate NP. Hence at that depth cooling had taken place through (V—v)*, represented by Pn. Now the compression which each layer of the crust undergoes is caused by the contraction of all - the matter beneath it. Let r be the present mean radius of the earth; E the cubic contraction for 1° F. Hence the layer of the sphere at 1 ¢¢ Phil. Trans. Royal Soc.” 1873, Vol. 163, p. 199. COMIC OOOKS.EO