Pond. — On Strata from Mount Eden. 407 



mentioning is the increase of lime in the upper beds, pointing to a gradual 

 infiltration from some of the volcanic beds of later deposition. 



I cannot help thinking that this subject sadly needs the attention of some 

 of our geologists more particularly, and that in so doing a rich field would be 

 brought before them. Dr. Hochstetter, speaking on extinct volcanoes, and 

 particularly of this locality, instances the rising of Monte Nuovo, near Naples, 

 which in two days and nights grew to the height of 400 feet, and remarks, 

 " we may venture to say that cones, such as Mount Eden, are likely to have 

 sprung up in the course of a few days." 



Now, from Mr. Firth's researches we have seen that this volcano, when 

 in action, must have been intermittent to have allowed time for the deposition 

 of the vegetable-bearing strata b and a, with the volcanic ash between them, 

 and for the clothing the same on each occasion with vegetation before its 

 instant destruction by the hot debris. But with respect to the several 

 eruptions later than this period, and mentioned in Mr. Firth's paper to the 

 number of five, I think it is very probable that they will, on examination, 

 resolve into a smaller number of perhaps very short duration, as in the 

 presence of so many craters, and in this instance so close to the base of the 

 largest, enormous masses would be ejected, taking the form of scoria, ash, or 

 mud, as the absence or presence of water with the consequent steam and 

 terrific pressure would determine. To decide this question, however, great 

 care would have to be exercised in the examination of the surfaces of the 

 different strata, as in many instances minerals when first ejected in volcanic 

 matter are in the state of sulphides or sulphurets, which, by exposure to the 

 action of air and water for any length of time would become oxidized, and, 

 in the presence of iron, immediately discernible. By this means a very close 

 approximate to time could be made in many instances, giving reliable data as 

 the basis for future calculations on this very interesting subject. 



