150 EIGHTH REPORT — 1838. 



slices of fossil teeth to a determination of the natural family, or genus, 

 to which such teeth had belonged, when other characters fail, or a 

 complete tooth is unattainable. Finally, Mr. Owen remarked, that 

 through the endless diversity which the microscopic texture of the 

 teeth of different animals presented, the universal law of the tubular 

 structure could be unequivocally traced ; and that the general tendency 

 of the modifications observable in descending from man to the lower 

 classes of the vertebrate animals, was a neai-er approximation of the 

 substance of the tooth to the vascular and organized texture of bone. 



MECHANICAL SCIENCE. 



On the Use of Wire Ropes m Deep Mines. By Count Augustus 

 Breunner. 



There had been introduced into the silver mines of the Hartz Moun- 

 tains, about seven years ago, ropes composed of twisted iron wire, as a 

 substitute for the flat ropes previously in use. Since that time they 

 have been adopted throughout the mines of Hungary and most of those 

 in the Austrian dominions, to the almost total exclusion of flat and 

 round ropes made of hemp. These iron ropes are of equal strength 

 with a hempen rope of four times the weight. One has been in use 

 upwards of two years without any perceptible wear, whereas a flat 

 rope performing similar work would not have lasted much more than a 

 single year. The diameter of the largest rope in ordinary use in the 

 deepest mines of Austria is one inch and a half. This rope is com- 

 posed of iron wires, each two lines in diameter ;_^j;e of these are braided 

 together into strands, and three of these strands are twisted tightly into 

 a rojoe. Great care is requisite in making the rope that the ends of 

 the wires be set deep in the interior of the rope, and that no two ends 

 meet near the same part. The strength of these ropes is little less than 

 that of a solid iron bar of the same diameter. The usual weight lifted 

 is 1000 lbs. The rope on leaving the shaft must be received on a cy- 

 linder of not less than eight feet diameter, and be kept well coated with 

 tar. There is a saving of about one-third of the power in one case 

 mentioned, for four horses with a wire rope are doing the same work 

 as six horses with a fiat rope. It was suggested by Count Breunner, 

 that the substitution of iron ropes for the flat ropes in our deep mines 

 and coal-pits would be attended with the same, if not greater ad- 

 vantages than have attended their introduction into the mines of the 

 Austrian dominions. 



On the Timber Viaducts now in progress on the Newcastle and North 

 Shields Railway. By B. Green. 



The object of this paper was to give a description and explanation 

 of the principle of constructing timber bridges on a more durable, 



