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peculiar difficulties. The diamonds that are used are not valuable gems, but 

 carbonate, a substance that till lately had no commercial value, and was first 

 introduced for the purpose of cutting other diamonds. It differs from the 

 brilliant diamond in being very imperfectly crystallised, which also gives to 

 carbonate its value for drilling purposes, as it has next to no cleavage, and 

 consequently does not split up or break in the way that a diamond or piece of 

 boart would do. The application of the diamond to rock-drilling is worked 

 out as follows : — The stones are set in an annular ring made of steel ; they 

 are fastened in by making holes as nearly as possible the size of the stones to 

 be set, and then burying them, leaving projecting only the amount necessary 

 to allow the water and debris of the cutting to pass ; the metal is then drawn 

 round the stone so as to close it in on every side, and give as large a bearing 

 surface as possible to resist the tendency of the stone to be forced out. The 

 crown so set is attached to the end of a steel tube and kept rotating against 

 the rock at some 250 revolutions per minute. Water is supplied through the 

 hollow of the bar, whence it passes under the cutting face of the crown to 

 the surface of the hole between the side of the latter and the outside of the 

 boring tubes ; the diamonds are thereby kept cool, and the debris from the 

 cutting is washed away. The crown has to be kept pressed forward with a force 

 depending on the nature of the rock to be cut, varying from 400 lbs. to 800 lbs., 

 when the cutting is done at speeds varying from 2 inches to 4 inches per 

 minute. Granite and the hardest limestone are readily cut at 2 to 3 inches per 

 minute ; sandstone at 4 inches ; and quartz at 1 inch per minute. The cutters 

 travelling in an annular ring, it follows that a core is produced, an arrange- 

 ment which, while it ensures a minimum of work being done to make a given 

 sized hole, affords evidence of the strata passed through, a fact which is in- 

 valuable for certain applications. 



GEOLOGY. 



Paleontology. — Mr. Ray Lankester has described a new form of hetero- 

 stracous fish-shield, which is intermediate in form between Scaphaspis and 

 Ptcraspis. The specimen, which he names Holaspis sericeus, is figured in the 

 " Geological Magazine," and was discovered in the grey cornstone, of Old 

 Red Sandstone age, near Abergavenny. 



Professor Owen has communicated to the Geological Society the description 

 of a fossil dentigerous bird, which he names Odontoptcryx toliapiais. From a 

 consideration of all the characters furnished by the remains, which were 

 obtained from the London clay of Sheppey, he concluded that it was a warm- 

 blooded feathered biped with wings ; that it was web-footed and a fish eater, 

 and that in the catching of its prey it was assisted by the pterosauroid armature 

 of its jaws. He indicated the characters separating Odontopteryx from the 

 cretaceous fossil skull lately described by Professor O. C. Marsh,* and which 

 be affirms to have small similar teeth implanted in distinct sockets. 



Professor Duncan, continuing his researches on the fossil corals of the West 

 Indies, has now described those from the Eocene formation. He remarks that 

 the affinities and identities of the fossil forms with those of contemporaneous 

 reefs in Asia and Europe, and the limitation of the species of the existing 

 Caribbean coral fauna, point out the correctness of the views put forth by 

 S. P. Woodward, Carrick Moore, and himself concerning the upheaval of the 

 Isthmus of Panama after the termination of the Miocene period. 



In an address to the Natural History Society of Montreal, Dr. Dawson has 

 discussed the geological distribution of the oldest known fossil, Eozbon 

 Canadense and allied forms. He mentions its occurrence in rocks of 

 Huronian age in Ontario and Bavaria; in the Middle and Upper Cambrian 

 there are few limestones likely to contain such a fossil, but in Labrador species 

 of ArchcEocyatlnis are found, one of which he has ascertained to be a calcareous 

 chambered organism of the nature of a foraminifer, though there is little 

 doubt that others are, as Mr. Billings has shown, allied to sponges. In the 

 limestones of the Trenton group (Lower Silurian) animals of the Eozoon type 

 occur abundantly. The concentrically laminated fossils which sometimes 



* Vide Quart. Journ. Science, No. xxxviii., April, 1S73, p. 272. 



