﻿410 Henry R. Hoivorth — Geology of the hie of Man. 



(Fig. 1, No. X.), sparkling like the scales of a fish, also excited much 

 curiosity among the natives. 



The siliceous ironstone is very difficult to fuse in crucible experi- 

 ments with the usual proportion of limestone fluxes, even in the 

 intense heat of a puddling furnace ; but I found the blue Lias Clay 

 an excellent flux, deducting of course the iron it contains (about 

 four per cent.) from the result. Fossils were very scarce, and 

 only the usual Inferior Oolite specimens, with a few small phosphatic 

 nodules being occasionally met with of about an inch in length by 

 half an inch in diameter, in the Northampton Ironstone bed. 



Several chalybeate springs find their way into the valley, and form 

 thin patches of re-deposited iron. ore. The dead leaves and twigs at 

 the bottom of ditches being sometimes covered with crystalline 

 feathers of peroxide of iron, as bushes and trees are occasionally 

 decorated with hoar frost in winter. 



IV. — Geology of the Isle of Man. 

 By Henry H. Howokth, Esq. 



IN a recent visit to the Isle of Man, I spent three long days in 

 examining the deposits of the very interesting district in the 

 south of the island, and I wish to draw the attention of your readers 

 to some facts which are, I think, important. Not being an ex- 

 perienced geologist, I hope I shall do so with becoiaiing modesty, 

 and I should feel very gratified if some more practised geologist 

 would verify my statements, which are, however, not rashly made, 

 as I have sifted the question with care and patience. 



Mr. Gumming has written the most elaborate account of the 

 geology of the Isle of Man, and his work on the island is an admir- 

 able specimen of what such a work ought to be. He is the authority 

 for the opinion now generally received, that the Mountain Lime- 

 stone which occurs under very interesting circumstances in the bays 

 of Derbyhaven, Gastletown, and Poolvash, is separated from the 

 underlying schists by deposits of the Devonian or Old Eed Sand- 

 stone period. This conclusion, if true, would be very interesting in 

 view of the recent discussions as to tho relations of the Old Red 

 Sandstone to the Garboniferous formation, since it is admitted by Mr. 

 Gumming that the fossils contained in these red rocks are identical 

 with those contained in the limestone. 



I believe the view of Mr. Gumming on this subject to be entirely 

 erroneous, and that the red rocks in question do not belong to the 

 Old Eed formation, nor are they older than the limestone, but that 

 they in fact overlie that formation. There are four ways in which 

 the age of the deposit may be tested, and the result in every case is 

 conclusive that it is not Devonian. 



First, the paleeontological evidence. Into this I shall not enter. 

 Mr. Gumming admits that the fossils found in the red deposit are 

 the same as those found in the limestone, and this fact is assuredly 

 a ■priori almost conclusive that the red rocks are not Devonian. 



Secondly, the petrological evidence. The rocks in question consist 



