368 



THE GEOLOGIST. 



poraiieous — as formations acted upon by processes affecting the 

 whole earth's surface at the same time. If our supposition be cor- 

 rect, they are only the everywhere tolerably analogous consequences 

 of local eruption, which may have been very far separated from each 

 other by time. The baryte-veins at Freiberg, in the Thiiringer 

 Wald, and in the south of France, may belong to very different 

 geological epochs ; they are to be considered, wherever they are 

 found, as representing the same stadium of local eruptive activity. 

 The same holds good for the regular succession of minerals found in 

 veins, druses, and amygdaloids ; the same series may have repeated 

 itself at very different times. The stages of this series cannot, 

 therefore, be used generally to define age like those of the 

 sedimentary formations ; they intimate only the relative age of the 

 isolated local process of formation. 



We shall now endeavour to apply these general theories to the 

 more essential phenomena of the Freiberg ore-veins. 



(To be conf,i?med) . 



NOTES AND QUERIES. 



Tield-Meetings op the Geologists' Association. — Sir, — In the last 

 number of your excellent magazine a letter appeared, in which a suggestion 

 was brought forward that it woidd be well for the Geologists' Association to 

 institute occasional field-meetings. Such a course would be, without doubt, 

 exceedingly advantageous, as it would tend to make the members better 

 acquainted with each other, and to increase their interest in the science. For 

 my own part I should be very glad to see the plan adopted, knowing that a 

 lecture giving at a natural section and on the fossils in situ is far more valuable 

 and instructive than one illustrated by the most expensive diagrams. The 

 commxittee of the Geologists' Association, however, feel they are not in a posi- 

 tion to carry out the proposal during the present year ; but they hope, and 

 they have deputed me to make this statement, tliat during the next they shall 

 be able to invite the members to a geological ramble, and to spend a summer's- 

 day both pleasantly and profitably. — I am, Sir, youi's faithfully, Thomas 

 Wiltshire. 



Artificial Origin of Hock-Basins. — In your magazine, valuable on 

 account of the popular style in wliich it treats our beautiful science, I was last 

 month very pleased to read the remarks of Mr. Rupert Jones on the weathering 

 of granite, and especially that portion of them referring to the rook-basins of 

 Dartmoor. Having been born and brought up in the neighbourhood of this 

 district, I happen to know the rock-basins, logging-stones, and cheese-shaped 

 granite-rocks well ; and it is because I am obhgecl to take exception to the 

 remarks of Mr. Rupert Jones on the formation of the " rock -basins," that I 



