240 ANNUAL OF SCIENTIFIC DISCOVERY. 



Otoliths occur in the tertiary beds much more abundantly than any 

 other parts of fishes, and much more so than the teeth. This fact at 

 first sight may appear startling to the collector from the palaeozoic 

 rocks, when the commonest remains are the teeth, spinous defences, 

 and scales. But a little reflection will easily solve the apparent riddle. 

 In the Silurian, carboniferous, etc., seas, the principal inhabitants were 

 cartilaginous fishes, and the hardest and most indestructible portions 

 of their bodies were the teeth and spines ; whereas in the later tertiary 

 beds the osseous fishes predominated, which do not possess the fin- 

 spines or solid crushing teeth. Of them the hardest parts are the ear- 

 bones in question. 



The appearance of the otoliths is very different in appearance from 

 the bones of the fish ; they have a porcellaneous appearance, and quite 

 distinct from the semi-transparent bones of the cranium. The otoliths 

 of the fresh-water are much more rounded and globose than those of 

 the marine fishes. As objects for the binocular microscope, none are 

 more beautiful than these bodies ; among them may be recommended 

 those of the sprat, brill, smelt, anchovy, and gray mullet. 



GEOLOGICAL SUMMARY. 



The Origin of the Granites. At a recent meeting of the London 

 Geologists' 'Association, Mr. Tomlinson, after adverting to the close 

 resemblance or identity of the slags and dross of iron-furnaces with 

 naturally formed volcanic rocks as lavas, pitch-stones, etc., stated, 

 that while we may regard the plutonic origin of such rocks as certain, 

 it should be borne in mind, that volcanic rocks formed but a very small 

 proportion only of the rocks termed plutonic or fire-formed. All gran- 

 ites and certain porphyries were generally regarded as having been 

 fused by such action at great depths. But as many of these plutonic 

 rocks contained magnetic iron-ore they could not be the results of 

 fusion, else their composition would be that of a vitreous instead of 

 crystalline rock. In cooling, quartz and iron would not separate, the 

 oxides having a strong affinity for silica. Another difficulty which 

 presented itself to the mind of the plutonist was that fossil forms were 

 occasionally met with in magnetic iron-ore, as the Devonian brach- 

 iopod, Spirifer speciosus, which was thus found, in a quartz rock, mixed 

 with iron-pyrites. Such facts pointed more to a neptunistic than a 

 plutonic origin for granite, quartz, and the allied rocks. 



Professor Morris commented at considerable length upon the sub- 

 jects touched upon in Mr. Tomlinson's paper. He described the evi- 

 dences, chemical, mineralogical, and dynamical, which favored the 

 conclusion to which most geologists had now come that granite and 

 the allied rocks were formed under conditions dissimilar from those 

 which obtained at or near the surface of the earth. Water at a high 

 temperature was probably an important feature in these metamorph- 

 isms ; indeed, so important was it deemed by Professor Haughton, that 

 he had proposed to divide the granites into hydro- and pyro-uietamorphic 

 groups. 



The Origin and Subsequent Alteration of Mica- Schist. Mr. II. C. 

 Sorby, in a paper on this subject, recently presented to the London 

 Geological Society, stated, that when ripples are formed whilst mate- 

 rial is being deposited, a structure is generated which is termed "ripple- 



