GEOLOGY. 177 



crease in superimposed strata should be inversely as their 

 conductivities;" so that the more rapid increase of tempera- 

 ture in the upper 700 feet of the Sperenberg boring may be 

 attributed to the relatively small conductivity of the gyp- 

 sum and anhydrite. It is not impossible that heat evolved 

 during the hydratation of the latter may have contributed 

 to this result. 



Careful observations by Symons in a boring near London, 

 at a depth of 1000 feet, extending over a period of eighteen 

 months, show that the temperature at that depth, as might 

 be expected, suffers no perceptible changes. 



TERTIARY FORMATION OF THE ARCTIC REGIONS. 



In connection with the discussion in the Record of last 

 year (page cii), it may be noticed that Fr. Schmidt has sum- 

 med up our knowledge of the Tertiary geology of the North. 

 The Miocene there shows a great continental area character- 

 ized by coal-seams and by a rich fauna, and is traced from 

 the Amoor basin into Kamtchatka, Alaska, Vancouver's Isl- 

 and, and eastward as far as Mackenzie River, Greenland, and 

 Spitzbergen. The Pliocene was a marine deposit, and is not 

 known in continental Siberia, but occurs in Sakhalin Island, 

 in Kamtchatka, and the Aleutian Islands, and extends to Ore- 

 gon and California. Of its fauna the greater number of spe- 

 cies inhabit to-day the North Pacific, but some are found 

 only in the Polar Sea and the North Atlantic. He concludes 

 that the fauna of the two oceans was then more alike than at 

 present, and that these were then more closely connected 

 through the Polar Sea. 



o 



FOSSIL FLORAS. 

 Heer, from his studies of the fossil floras of Greenland and 

 Spitzbergen, concludes that the facts are against a gradual 

 transformation of plant-types, since, in the Upper Cretaceous, 

 dicotyledons suddenly appear in great variety, while other 

 forms at this period disappear as rapidly. He supports the 

 view of an arctic origin and a southern migration of plants, 

 and declares that his investigations of the northern fossil 

 floras do not indicate any alterations of climate or former ice- 

 periods in these regions. He thus confirms the conclusions 

 of Nordenskjold as stated in the Record for 1S7G (page cii). 



H2 



