294 Progress in Science. [April, 



way. Mr. Barker employs hydraulic power to apply the brake-blocks to the 

 wheels, and according to his plans each carriage has a main water-pipe running 

 its entire length, and which is provided with branches leading to small 

 hydraulic cylinders, a length of india-rubber tubing being used to connect each 

 of these cylinders with the corresponding branch pipe. There is an hydraulic 

 cylinder to each wheel, to which brake-blocks are applied, the ram with which 

 the cylinder is fitted being connected to the brake-block nearest to it, while the 

 cylinder itself is coupled, by a pair of rods, to the brake-block on the opposite 

 side of the wheel. The cylinder is supported by the brake-hangers, and the 

 water under pressure being admitted to the cylinder at the end furthest from 

 the wheel, acts upon that end and upon the ram, thus forcing the brake-blocks 

 into contact with the opposite sides of the wheels. This arrangement ensures 

 uniformity of pressure on the blocks, and the thrust of one block being resisted 

 by that of the other, no strain is thrown upon the axle. 



GEOLOGY AND PALEONTOLOGY. 



Eozoon Canadense. — The genuine organic character of this oldest known 

 fossil having recently been attacked, has brought a resume of the grounds for 

 so considering it from Dr. Carpenter and Professor Dawson, of Montreal. To 

 the objection that it has hitherto only been found in metamorphic and structur- 

 ally altered rocks, in which it would scarcely be possible for an organic -structure 

 to be preserved, Dr. Carpenter replies that the eozoonal structure is most 

 characteristically displayed in those portions of the serpentine limestone of the 

 Laurentian formation which have undergone the least metamorphic change. 

 Principal Dawson also states that several other Foraminiferal forms allied to 

 Eozoon which have recently been discovered in the Laurentian rocks of 

 Canada, will shortly be described. 



Duration of the Cretaceous Epoch. — Professor Wyville Thompson has recently 

 propounded the theory that " we may be said to be still living in the cretaceous 

 epoch," a view to which Dr. Carpenter has also lent his support. The argu- 

 ments in favour of this theory rest, not only on the deposition over a large part 

 of the North Atlantic sea-bed, at the present time, of a sediment closely corres- 

 ponding with the chalk, and of the occurrence in it of a few types of life like 

 the Lingulce and Terebratulidce belongingto the older formation ; but by the 

 pesistence of those which constitute the formation itself, viz., the Globigerince, 

 the coccoliths, and the coccospheres ; as also of numerous types of Echino- 

 dermata that were formerly considered essentially cretaceous, and of a great 

 variety of those sponges (including Zanthidia) and Foraminifera, whose 

 abundance in the white chalk is one of its most important features. 



The exact part played by the Gulf-stream in the heating of the North 

 Atlantic Ocean and the western shores of Europe above the normal tempera- 

 ture of their latitude, though belonging more strictly to Physical Geography 

 than to Geology, has yet an important bearing on the above subject. Dr. 

 Carpenter believes that the direct influence of the Gulf-stream terminates with 

 the latitude of the Bay of Biscay, and considers it an open question, whether 

 the super-heating of the surface-water observed on a hot midsummer day 

 beyond the northern border of the Bay of Biscay is not as probably due to the 

 direct influence of the sun as to the extension of the Gulf-stream to that 

 locality. This current he does not believe to extend to the Channel between 

 the North of Scotland and the Faroe Islands. Professor Wyville Thomson, 

 on the other hand, adheres to the older belief of the direct influence of the 

 Gulf-stream on the climate of north-western Europe ; an opinion which is 

 shared by the eminent geographer Dr. Petermann, who maintains that there 

 is no longer a shadow of doubt as to the existence of a movement of warm 

 water, be it called a drift or a stream, from the Tropics obliquely across the 

 Atlantic Ocean towards the Arctic regions. Dr. Carpenter states that the 

 temperature-soundings taken in the " Porcupine" expeditions of 1869 and 1870, 

 conclusively show that a temperature as low as 36-5° F. prevails over the deeper 

 parts of the North Atlantic sea-bed ; in connection with which the statement 

 becomes of great interest which was made by Mr. Gwyn Jeffreys, at the recent 



