11G REPORT 1859. 



Lossiemouth, at Spynie quarry, and at Findrassie quarry, have afforded reptilian 

 remains of such a nature as to show considerable affinity to the palaeontology of 

 the Trias. Notwithstanding this circumstance, there is strong reason to infer that 

 the strata in the district are the representatives of the upper portion of the Old 

 Red Sandstone series. From an examination of the several localities where the 

 rocks are exposed north of Elgin, Professor Harkness has been induced to adopt 

 the conclusions of Sir Roderick Murchison, and other geologists who have inspected 

 this neighbourhood, and has arrived at the inference that the strata here appertain 

 to the Old Red Sandstone formation. From the ridge in which the Bishops' Mill 

 quarries occur, immediately north of the river Lossie, and where Holoptychian 

 fishes are found, to Spynie hill, there is a constant N.N.W. dip at about 10°, and 

 the lithology of the deposits, as exposed in this interval, shows an intimate relation 

 among the arenaceous rocks which occupy this area. The rocks are to a con- 

 siderable extent masked by debris ; but whenever these are apparent, they manifest 

 no traces of faults of such an extent as would disconnect the Holoptychian yielding 

 strata from the reptilian beds which occur in this portion of Moray. 



On the Origin of the Ossiferous Caverns at Oreston. 

 By Henry C. Hodge. 



The author referred, in the first place, to the description of this cavern given 

 by Mr. Whidby, and continued : — 



" The statements so confidently made by Mr. Whidby as to the perfect enclosure 

 of the caverns by solid limestone, have been confirmed by my own observations, 

 and this fact has not failed to surprise even the workmen engaged in the quarry j 

 but it must be evident that at some period an opening did exist, and it occurred 

 to me that such might be most successfully sought for between the surfaces of the 

 beds of which the masses of limestone are composed, No satisfactory conclusion 

 could be drawn from caieful examination of the rock during the opening of the 

 cavern ; but on looking narrowly into the beds of limestone in the progress of the 

 workings, it was found that a thin seam of purple calcareous clay-slate was inter- 

 posed between the neighbouring beds of limestone, at about the same parallel as 

 that in which the caverns were met with. On further investigation, it was dis- 

 covered that alternations of this purple slate with the limestone were not unfre- 

 quent, but the laminae of slate were in most cases so intimately blended with the 

 limestone beds, as to form really a solid mass of compact rock ; and on looking 

 into the structure of the more evident layers of the slate, it was ascertained that 

 in some parts they were much more calcareous than in others, and that small por- 

 tions of limestone, having similar physical characters to those of the surrounding 

 rock, were interspersed at varying intervals. In other places, the slaty layers 

 were in a state of decomposition, red and reddish white clay being formed as its 

 result ; and on tracing a layer of this kind through the side of a cavern laid open 

 during the workings, it was seen that portions of it were so disintegrated as to be 

 easily pulled from their position, the seam being, in its most solid portions, com- 

 posed merely of layers of limestone fragments with interposed clay and red sand, — 

 the whole, apparently, kept in place by the accidental infiltration of calcareous 

 matter. Here, then, were facts that might enable me to account for the clay 

 found in the caverns, and afford a means through which the beds of limestone may 

 have been caused to separate from each other. Again, it was discovered that 

 some of the hollows in the adjoining limestone were stained with a black earthy 

 substance, found, on analysis, to be composed of the peroxides of iron and man- 

 ganese, these having evidently proceeded from the decomposition of a variety of 

 dolomite very generally present in this limestone, — not exhibiting, however, any 

 definite mode of deposit .in it, but passing through its beds in the most irregular 

 manner. From these phenomena, it appeared reasonable to conclude that the 

 decomposition of the slate in the layers, through the combined agency of water 

 and carbonic acid, had opened a communication with the external air to the above- 

 named irregular masses of dolomite (the unchanged limestone fragments of the 

 slate serving to keep the beds from close contact with each other), and that, in 

 this way, the carbonates of iron and manganese contained in them had been con- 

 verted into peroxides, and the evolved carbonic acid proceeding from their decom- 



