98 PROCEEDINGS OF THE ACADEMY OF 



Dr. Leidy stated that on last Saturday, in company with Dr. Darrach, he had 

 visited, to them, anewandrich botanical locality, which was worthy of the atten- 

 tion of those members interested in our local flora. This was at Jackson, N. J. 

 about 20 miles from Philadelphia, on the Camden and Atlantic Railway. A 

 cedar swamp, crossed by the latter, not one hundred yards from the station, 

 contains the greatest profusion of Saracenia purpurea, and Helonias bullata, 

 which is now in flower. Near by, they also found abundantly the Pyxidan- 

 thera and Cassandra both in flower. Oxycoccus, Drosera, etc., were also 

 noticed. The neighboring extensive forest tract is thickly carpeted with Gaul- 

 theria procumbens. 



Prof. W. B. Rogers communicated the result of observations which he had 

 made within the last year on the structural and geological relations of the Al- 

 bertite or so-called Albert Coal of New Brunswick. 



An examination of the mine afforded, as he thought, convincing proof that 

 this remarkable accumulation of asphaltic matetial could not have formed a 

 part of the regular carbonaceous deposits of the region, that it is not and 

 never has been a true bed or stratum, but that it should rather be regarded as a 

 mass collected within an irregular fissure of subsequent formation, by the dis- 

 tillation or infiltration of asphaltic matter from the surrounding bituminous 

 shales. 



The principal features of the deposit pointing to such an origin are the very 

 limited extent of the mass longitudinally traced, its sudden and great irregular- 

 ities of thickness and trend, and the yet more striking fact of its transverse direc- 

 tion in many parts of its course as compared with the bedding of the adjacent 

 rocks. In the lower level at a depth of about four hundred and sixty feet where 

 the combustible material has been removed almost entirely from end to end, the 

 slaty rocks are seen in many places abutting against the sides of the mine at 

 a steep angle, presenting frequently a jagged surface, such as would result from 

 a transverse fracture and gaping of the strata. The Albertite was seen adhering 

 to these irregular surfaces, as well in the cavities as on the projections, affording 

 even in hand specimens excellent examples of the discordance of the mass as to 

 position with the stratification of the contiguous rocks. 



It is worthy of note that the material thus adhering to the walls of the mine 

 has none of that intermixture with earthy sediment which so often marks the 

 contact of regular coal seams with the enclosing strata, but maintains the same 

 remarkable ( purity as in the midst of the mass. It is, moreover, quite free from 

 the carbonaceous and rocky debris, and other marks of mechanical violence, 

 which it must have presented had it originated in the dislocation and displace- 

 ment of a coal seam originally conformable with the stratification of the neigh- 

 borhood. 



These evidences of the nature and origin of the deposit are confirmed bjthe 

 statement that in the progress of the mining, several large fragments of the verti- 

 cal wall-rock have been found detached and imbedded in the midst of the Alber- 

 tite, and on one occasion a mass of unusually great dimensions could be traced 

 by correspondence of form to a cavity in the wall at some distance above, from 

 which it would seem to have fallen, while the contents of the fissure were still 

 but imperfectly solidified. 



The conclusions of Prof. Rogers, as to the origin and nature of this remark- 

 able deposit are thus completely in harmony with those which Prof. Leidy ha? 

 maintained on the ground of a microscopic examination of the material. 



Prof.W. B. Rogers gave an account of some experiments in binocular vision, 

 which he had devised for the purpose of testing the theory of the successive 

 combination of corresponding points as maintained by Sir David Brewster. 



In one class of these experiments two slightly inclined luminous lines were 

 combined into a perspective resultant, either with or without a stereoscope. On 

 looking at this intently for a few seconds, so as to induce the reverse ocular 



[April. 



