476 Irdelligence and Miscellaneous Articles. 



The intrusive Teappeai^ rocks, which are regarded as influencing 

 the production of auriferous veinstones in the Devonian and meta- 

 morphic rocks, are noticed at considerable length by the author, and 

 consist of pyritous porphyrites and porphyries, pyritous diorites and 

 diabases, chrome-iron serpentines and pyritous felsites ; the author 

 considers that this order probably indicates the succession of these 

 rocks in time. The veinstones he thinks were probably deposits of 

 mineral matter from the hydrothermal action which preceded, ac- 

 companied, and continued long after the cooling of the traps them- 

 selves. 



The VOLCANIC EOCKS, in the author's opinion, have played a most 

 important part in determining the elevation and present physical 

 outline of North-eastern Queensland ; they follow the line of greatest 

 elevation on the main watershed at altitudes of from 1500 to 2000 

 feet above the sea-level. The general arrangement of the other 

 rocks referred to is epitomized by the author as follows : — 



"With the exception of the M'^Kinlay ranges, a line drawn par- 

 allel with the eastern coast at a distance of 250 miles would include 

 all the Palaeozoic, metamorphic, granitic, Trappean, and volcanic 

 rocks represented in the colony, both coal-groups lying within the 

 same area. 



" The Mesozoic and Cainozoic systems occupy the surface-area to 

 the westward. 



"The descent going eastward is first locally a thin capping of 

 * Desert Sandstone,' next Carboniferous, then Devonian and possibly 

 Silurian, with patches of metamorphic and granitic rocks interspersed. 



" The chief granitic mass extends from Broad Sound to Cape York, 

 with an occasional capping of ' Desert Sandstone.' " 



The paper contained numerous analyses of the various rocks ; and 

 the fossils have been worked out by Messrs. Etheridge and Carruthers, 

 whose lists and descriptions of them are appended to the paper. 



LVIII. Intelligence and Miscellaneous Articles. 



ON THE COLLISION OF ELASTIC BODIES, AND A NUMERICAL 

 VALUATION OF ITS DURATION. BY H. SCHNEEBELI *. 



COLLISION has long been studied and in divers manners, but 

 always with respect to its influence on the bodies which take part 

 in it, and not with reference to the duration of their contact; this has 

 hitherto been entirely neglected, it having been taken for granted 

 that the duration was excessively small and difficult to measure. It 

 is precisely the study of this question to which M. Schneebeli has 

 devoted himself. He has applied a method devised, for this kind of 

 researches, by Pouillet, and which consists in profiting by the con- 

 tact to close a galvanic circuit, and deducing its duration from the 

 galvanometric deflection produced by a known current which 

 traverses the circuit during the whole time of contact. 



For this jDurpose the galvanometer must previously be calibrated — 



* Pogg. Ann. vol. cxliii. p. 239. 



