170 



HARDWICKE'S SCIENCE-GOSSIP. 



being excessively acute. These, by some, would be 

 considered different species ; as, for instance, the 

 ovate A. adiantum nigrum has been called A. 

 obtusum, while the acute variety goes by the name 

 of A. acutum. Here, however, in both the Ruta 

 muraria and in the Adiantum nigrum, every grada- 

 tion between the obtuse and the acute forms are 

 found, but the normal form of the country for both 

 species is the semi-acute. The obtuse varieties 

 seem to be most uncommon, growing on open 

 crags and cliffs that have a south aspect ; while the 

 typical acute forms seem to affect north aspects ; and 

 in places looking S.E., E., and N.E. are found the 

 intermediate forms. C. officinarum also has'many 

 varieties ; a handsome one having a very luxuriant 

 foliage, the pinnae being so large and close that they 

 overlap one another, and if their margins are serrated 

 the plant is very handsome. A peculiar variety, in 

 places not uncommon, has marked intervals, between 

 small pinnse, the latter being deeply serrated. One 

 variety of A. trichomanes has its pinnse so deeply 

 cut that it might nearly be mistaken for A. fon- 

 tanum ; while of S. vulgare there is a lanceolate 

 variety that has a conspicuous marginal rib, the edge 

 outside which is serrated. This] last variety grows 

 well, and greatly improves when cultivated. A. 

 capillus veneris, although liking a limy soil, is one 

 of the marine ferns, and usually only occurs in the 

 immediate vicinity of the sea. Mr. Foot, however, 

 found it growing inland in two places, in one of 

 which, although the plants were neither numerous 

 nor very luxuriant, yet the pinnse were very large, 

 some being the size of a florin-piece. In the deep 

 open joints of the limestone crags adjoining the sea 

 it is wonderful to find the length to which the 

 fronds of A. marinum grow, all being between 2 ft. 

 and 3 ft. long, and as fine as any to be got at 

 Madeira. Here it should be pointed out that a 

 peculiarity of the ferns of the Burreu is the great 

 length of their stipes, some of the A. adiantum 

 nigrum having fronds over 2 ft. long, many of those 

 of the C. officinarum being from 9 in. to 12 in., while 

 the fronds of others are in proportion. The 

 Osmunda regalis, Mr. Eoot states, is only found on 

 some patches of coal-measures that cap the carboni- 

 ferous limestone. V. lobatum var. Lonchitidoides 

 is very fine and abundant, and might easily be mis- 

 taken for Polystichum lonchitis. 1 



THE ORIGIN OP GREENS AN DS.l 



TV/TR. S. A. STEWART does not appear satisfied 

 ^*- with my comments on his remarks concerning 

 "the Greensand and its Origin." In Science- 

 Gossip" for April (No. 13G), he quotes the para- 

 graph from my article, and offers to bury his 

 tomahawk if I consent to read " cannot be " for the 

 words "have not yet been" m the first sentence. I 



am quite willing to make the alteration he suggests, 

 but nevertheless I entirely fail to see how that 

 would bring his opinions into greater accord 

 with mine. I am ready to admit that the Irish 

 Geeensands are not composed of foraminiferal 

 casts ; but the admission only seems to me to widen 

 the divergence between our expressed opinions. Mr. 

 Stewart considers that it is necessary for Dr. Car- 

 penter's argument "that all greensands should be 

 constituted of glauconitic casts of foraminifera," 

 and consequently that one exception would be fatal 

 to his theory. Now, I have already stated that I 

 regard this as an unwarranted assumption ; on this 

 point, therefore, I think we can only agree to differ. 



I may be allowed, however, to explain what Mr. 

 Stewart terms my errors. In the first place, he 

 considers that no one can be misled by Dr. 

 Carpenter's expression, " the Greensand deposit of 

 the Cretaceous Epoch." Mr. Stewart states this 

 to be "a definite term, referring not to a greensand 

 bed, but to the Greensand formation as a whole.' 

 It would have been more satisfactory had he 

 explained what he intended to convey by the term 

 " Greensand Formation." No such formation is 

 acknowledged in recent manuals of Geology. An 

 Upper Greensand is known, and [a Lower Green- 

 sand formation is known ; but these are separated 

 by 100 to 300 feet of Gault, and it is certainly not 

 usual to unite all these beds under the name of 

 the " Greensand Formation " ; nay, the very line of 

 division between the Upper and Lower Cretaceous 

 systems is drawn at present between the Gault and 

 Lower Greensand, and Mr. Stewart will surely not 

 ignore this fact. 



The truth is that the terms " Lower Greensand " 

 or "Greensand Formation" are, like all other litho- 

 logical names, very unsuitable appellations for 

 periods of geological time, and I am sure I echo 

 the wish of most geologists when I say that the 

 sooner they are discarded the better. 



Mr. Stewart next remarks that it has been pretty 

 well established, and is indeed admitted by me, that 

 the casts of shells occurring in the Cambridge 

 Greensand are derived from an older bed. Now, if 

 this fact had been established before the year 1875, 

 I should certainly not have written, and the Geo- 

 logical Society would probably not have printed, 

 fifty pages as an attempt to prove it. I am cer- 

 tainly likely to admit a proposition which I have 

 endeavoured to maintain in a publication, the 

 authority of which Mr. Stewart wisely esteems 

 superior to mine. 



He thinks that I must have read his first commu- 

 nication in a hasty manner, otherwise I could not 

 have imagined that he considered the fact of the 

 absence of certain fossils from the Antrim Green- 

 sand proved the non-existence of these fossils in any 

 other locality. Perhaps he will allow me to quote 

 his own words, from Science-Gossip, 1875, p. 243, 



