49.2 Intelligence and Miscellaneous Articles. 



cavities have been filled with various substances. But, lately, M. 

 Yolger has asserted that amygdaloids are merely metamorphosed 

 conglomerates of sedimentary origin. Indeed a closer examination 

 of these rocks shows the existence of three distinct varieties of them. 

 In the first, and by far the most common of these varieties, decom- 

 position has begun with the crystallized minerals imbedded in the 

 rock, changing them into amorphous nodules, and at last leaving 

 only the cavities in which they were included. The second variety, 

 of far scarcer occurrence, owes its origin to the filling up of pre- 

 existing cavities. Those of the third variety, in conformity with 

 M. Volger's views, are really metamorphosed conglomerates inclu- 

 ding geodes, which have originally been pebbles rolled by water. 

 Metamorphism and pseudomorphism act within geodes exactly in 

 the same way as on minerals included in veins or in solid rocks. 

 Amygdaloids are consequently only a particular stage in those 

 changes which rocks are continually undergoing. — Imperial Academy 

 of Sciences of Vienna, Meeting of February 12, 1863. 



ON THE MOTION OF CAMPHOR TOWARDS THE LIGHT. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



I have never had the slightest intention of misrepresenting Dr. 

 Draper, or of detracting from the merit due to his industry and skill. 

 But I deny that the paper which he published in your Magazine in 

 1840, or the volume which he published in 1844, contains the 

 true theory of the motion of camphor towards the light, or that I 

 ever admitted that it did so. The former contains a question which, 

 had it been followed out and properly tested by experiment, would 

 have led to the true theory ; but that it was not thus tested is proved 

 by the fact that in the volume of 1844 it was again published as a 

 question and nothing more. 



I now leave my claims and those of Dr. Draper to be settled by 

 persons who may feel interest enough in the subject to read my 

 papers and his volume. I think they will find that the latter, full 

 as it is of details of ingenious experiments, leaves one as much in 

 doubt at the end as at the commencement, and cannot possibly be 

 considered as the earlier and later steps of a successful inquiry. 

 Indeed it is so difficult to trace any consecutive steps that the volume 

 was viewed by me as a whole, and as containing the latest revised 

 opinions of the author. 



I remain, &c, 



King's College, London, C. Tomlinson. 



May 25, 1863. 



AfG 21, 13 



