1 86 Geological Society. 



limestone, equivalent to the highest tertiary limestone of Austria and 

 Hungary. Fichtel is quoted as the earliest and best geological writer 

 upon Transylvania, particularly as to the localities of shelly deposits 

 and salt springs ; and it is stated that from his work alone M Beudant 

 was enabled to compile a map of this country. 



For an account of the eastern chain of trachytes the author refers 

 to what he has already written in Dr. Daubeny's work on Volcanos : 

 he inclines to the supposition that the scoriaceous trachy tic porphy- 

 ries were erupted during the cretaceous or perhaps even during the old 

 tertiary period ; and he dissents from M. Beudant as to the possibility 

 of drawing any distinct line of demarcation between the trachyte and 

 porphyry in those places where these rocks are contiguous, although 

 when at great distances from each other he allows the dissimilarity 

 of their respective characters. A stratified, pumiceous and trachytic 

 conglomerate, it is stated, frequently overlies the salt in Transylvania, 

 and contains impressions of dicotyledonous plants, leaves, and fishes. 

 The extinct craters of St. Annalake and the solfatarra still burning in 

 the trachyte of Budoskegy, and the many acidulated and mineral 

 springs, are considered by the author clearly to indicate the recent age 

 of some of the volcanic phaenomena in this country, to the principal en- 

 trance of which, the Romans assigned the name of " Vulcan's Pass." 



A paper was then read, On the Astronomical Causes which may 

 influence Geological Phaenomena ; by J. F.W. Herschel, Esq. F.R.S. 

 F.G.S., &c., &c. 



The author states his object in this paper to be, an inquiry into 

 the possible geological influence of slow periodical changes in the 

 orbits of the earth and moon, such as have been demonstrated by 

 geometers to take place in consequence of planetary and solar per- 

 turbation. Such influence he regards as extending only to the pro- 

 duction of changes in the amount of the tides and their consequent 

 erosive action on our continents, and of periodical fluctuations in 

 the quantity of solar heat received by the earth, every such fluc- 

 tuation being of course accompanied with a corresponding altera- 

 tion of climates^ and therefore, if sufficiently extensive and con- 

 tinued, giving room for a variation in the animal and vegetable 

 productions of the same region at different and widely remote 

 epochs. 



The subject of the tides is first considered. Since any approach 

 of the moon to the earth produces an increase of the lunar tide in 

 the triplicate ratio of such approach, it follows that any diminution 

 of the moon's mean distance must produce an increase in the ave- 

 rage tide during the whole period that such approach subsists. 

 The mean distance of the moon is actually on the decrease, and has 

 been so for ages past, producing the astronomical phenomenon 

 of her secular acceleration. The mean amount of the tides, there, 

 fore, has long been, and will long continue to be, on the increase 

 from this cause, but the effect of it is shown to be confined to such 

 moderate limits as to be of no geological importance. 



The author next considers the possible effect of an increase in 

 the excentricity of the lunar orbit, which would affect not the ave- 

 rage 



