120 EEPORT— 1872. 



that their fangs had been gnawed. To this it had been objected that the Cavern con- 

 tained two ossiferous deposits — one, termed "Breccia," found only iu certain 

 branches, the other, known as " Cave-earth," much more widely spread and of less 

 atitiquity — that fragments of the former were in certain localities found incorporated 

 in the latter — that in all probability fossils had been occasionally washed out of the 

 Breccia and redeposited in the Cave-earth — and that the following was the problem 

 to be solved : — \\'as not tliis the history of the remains of Mucluiirodus found in 

 Kent's Hole ? In reply, the author stated that whilst the Breccia teemed with 

 fossils, they were the remains of bears only, that Ihey were in a diiferent mineral 

 condition from those found in the Cave-earth, and that the teeth of 3Iachairo(h(s 

 were in this respect identical with the latter — that whilst the fangs of the Ma- 

 cJiairodus-teeth. were certainly gnawed, there were in the Breccia no indications of 

 the hy»na, to which the work was no doubt to be ascribed (none of his teeth, or 

 his coprolites, or bones gnawed by him) ; but in the Cave-earth his remains were 

 more abundant than those of any other animal — that in the Wolf's Cave there were 

 no traces of the Ijreccia, either in sitir, or in incorporiited fragments — and that the 

 absence of marks of contusion or abrasion was incompatible witli the hypothesis 

 of dislodgement and re-deposition. 



The paper concluded with the following expression of opinion on the three 

 questions discussed : — 



1st. There is no reason for believing or suspecting that more than five canines 

 were found by Mr. MacEnerv. 



2nd. The evidence that more than one incisor was found by Mr. MacEnery is not 

 conclusive. 



f!rd. Machairodus latidens belonged to the era of the Cave-earth of Kent's Cavern. 

 There is at present no evidence that it belonged to the earlier period represented by 

 the "Breccia; " and should such evidence present itself hereafter, it will simply 

 prove that, li]:e Ursns spchcus, Machairodus belonged to both eras. 



P.S. Since this paper was ^vl■itten, a fine incisor of Mac/iairodiis latidens has been 

 found in Kent's Cavern, by the Committee appointed b}' tlie British Association to 

 explore the Cavern. It lay with the left lower jaw of bear in the uppermost foot- 

 level of the Cave-earth, and had teeth of hyajna, bear, and horse verticallj' below 

 it, thus confirming tlie conclusion already arrived at respecting its era. 



On a remarlahh Block of Lava ejected hy Vesuvius at the Great Eruption, 

 April 1872, irhich proves tlie formation of Silicates throitcjli Sublimation. 

 Bu Herr G. vost Eath, Bonn. 



The aggregates rich in minerals found in the strata of tuff on Monte di Somma 

 are known to all mineralogists. Most of these magnificent mineral aggregates are 

 no longer ejected by tlie volcano of to-day; but even now fragments of ancient 

 lava are to be found amongst the projectiles of the volcano, distinguished by larger 

 crystals of leucite than those in the more recent lava-streams and in the 

 scorite. 



It is of high geological interest to examine such evidence as may allow of newly 

 formed minerals being recognized. Thus the ordinary lava, with its manifold mix- 

 tures of minerals and the delicate crystals in its cavities, cannot be the product of a 

 simple cooling. Some of the crystals found in the lava were already in existence pre- 

 viously and were swimming in tlie stream, while some were crystallizing out of the 

 her}- mass during the progress of its solidification ; and, lastly, certain crystals appear- 

 ing in cavities indicate the cooperation of vapour which had been active in the igne- 

 ous magma. The distinction of the various formations of minerals is exceedingly 

 difficult in the ordinary lava and scoriaj, as in the flowing and cooling lava different 

 mineralogical processes may combine. A more fiivoural:ile condition for observa- 

 tion is presented when a mass of ancient lava has been subjected again to volcanic 

 activity, and has served partly ns a substratum, partly as the base for new minera- 

 logical formations. It is easier by far to distinguish such newly formed crystals 

 accurately from the original lava in the blocks c'jected than in the ordinary lava. 



The study of such matters is conducting us to the view that the quantities of 



