•' Sir John Evans, K. C.B. 5 



Mr. Jolin Evans's paper on "A Cranium and Jaw in the Slab 

 containing the ArchcBopteryx " was published in the Natural History 

 Review for July, 1865, but it was not until 1884' that Dr. Dames 

 described the second specimen of long-tailed Archceopteryx (obtained 

 for the Berlin Museum), in which the head and neck of the bird 

 are preserved with the jaws furnished with numerous pointed teeth, 

 fully confirminy; Sir John Evans's observations on the Archceopteryx in 

 the British Museum made twenty years earlier. Already in 1881 

 Evans had inspected the specimen in the Berlin Museum and re- 

 printed the article of 1865 with some prefatory remarks on the 

 peculiarities of the Berlin specimen. 



Another subject which engaged Mr. John Evans's attention as early 

 as 1866 was the consideration of a possible cause of climatal changes. 

 We are all aware that great changes of climate have taken place in 

 the northern hemisphere, and we have every reason to assume that 

 corresponding changes have in all probability taken place in the 

 southern hemisphere ; also periods of giaciation may account for 

 accession of cold, but it may be doubted if by any rearrangement of 

 land surfaces or of warm currents, like the Guli Stream flowing north, 

 a sub-tropical, or a warm temperate climate even, could be forced up 

 towards the Poles. Nevertheless, such a condition seems needed to 

 explain the fossil vegetation in Tertiary times met with in Greenland, 

 Arctic America, and Spitzbergen. Mr. Evans suggested that if the earth's 

 crust were composed of solid material of equal density and thickness, 

 and the interior were filled with fluid matter over which the shell 

 could freely move, and the whole were in uniform rotation upon an 

 axis, the hollow sphere being in perfect equilibrium, its axis and that 

 of its fluid contents would perpetually coincide. If, however, the 

 equilibrium of the shell or crust be destroyed by the addition of a 

 mass of matter, midway between the pole and the equator, the 

 centrifugal force of the mass of matter so added would gradually draw 

 over the shell towards the equator ; thus, though the whole sphere 

 continued to revolve around its original axis, yet the position of the 

 pole of the hollow shell would be changed by 45° and the whole 

 surface would have shifted from its original position to the same extent. 

 The axis of the hollow sphere would again coincide, and would continue 

 to do so until afresh disturbance took place. If instead of the addition 

 of fresh matter a portion of the shell were removed, a reverse move- 

 ment would result, and that part of the shell excavated would eventually 

 find its way to the Pole. An ingenious model to exhibit this was 

 shown before the Royal Society (March 15th, 1866); it illustrated 

 the changes produced on a moving wheel by the alteration in the 

 adjustment of the weights around its rim. The subject was ably 

 discussed at the time and subsequently at the Geological Society on 

 Eebruary 21st, 1877.^ 



In 1892 Sir John Evans gave evidence before the Royal Commission 

 on Metropolitan Water Supply. He then put in a statement with 



^ See Geol. Mag., 1884, Professor Dames on Archmpteryx, pp. 418-424, 

 PI. XIV. 



2 Geol. Mag., 1866, pp. 171-174, 183-185 ; 1877, p. 219. 



