HARD WICKE ' ^ S CIENCE - G O SSIP, 



79 



tt Head with a round spot on each side behind the 



eves. 



A. pumilio (Charp.). Thorax black, vvith two 

 blue lines in front ; hind lobe of prothorax elevated, 

 rounded; abdomen black, ninth segment blue (6), 

 and dark (?) ; pterostigma (5) dark in the centre. 

 England, Ireland. Length 10 lin. ; exp. 12 lin. 



A. ^/t;^rt!;/j (Vander Lind.). Thorax black, with two 

 blue lines in front (according to Charpentier, these 

 lines in the 9 are yellow) ; hind lobe of prothorax 

 narrow, much elevated ; pterostigma 'dark in the 

 centre ; abdomen black, incisures of segments spotted 

 with yellow, eighth segment all blue ; British islands 

 generally. Length 12 lin. ; exp. 14 lin. 



N.B. A.piiniilio and A. elegans have each a variety 

 of the female of an orange colour, the thorax without 

 anterior dark stripes. (Hagen.) 



A. ptilchelhim (Van der Lind.). Thorax dark 

 bronze, with blue lines ; posterior margin of the 

 prothorax divided into three lobes, the middle one 

 the narrowest and longest ; pterostigma dark in 

 centre ; abdomen dark bronze, with short blue 

 intervals ; second segment ( 5 ) blue with a forked 

 dark spot reaching the hinder edge ; abdomen of 5 

 with two blue spots at the end of each segment. 

 British islands generally. Length 12 lin. ; exp. 14 lin. 



A. puella (Linn.). Thorax dark, with blue lines; 

 prothorax divided as above, but with the middle lobe 

 sinuate ; pterostigma dark ; abdomen ( 5 ) blue with 

 bronze spots, a detached forked spot on the second 

 segment, and eighth segment all bronze ; in $ bronze, 

 spotted at joints of segments with lighter tint of 

 ground colour. British islands generally. Length 

 12 lin. ; exjD. 16 lin. 



A. vierciiriale (Charp.). Thorax dark ; ptero- 

 stigma dark ; posterior margin of prothorax rounded ; 

 abdomen (6) blue, spotted longitudinally with 

 bronze ; second segment \vith a peculiarly-shaped 

 trifid spot reaching the liinder edge ; in j , all 

 bronze ; tenth segment in both sexes with a broad 

 notch. England. Length 10 lin. ; exp. 14 lin, 



A. cyathigerum (Charp.). Thorax blue ; posterior 

 margin of prothorax rounded; abdomen (6) blue 

 spotted with bronze ; second segment with a heart- 

 shaped spot reaching the hinder edge ; eighth seg- 

 ment nearly all bronze ; ( 5 ) also spotted with blue, 

 but bronze predominating ; eighth segment with a 

 stout spine on the under side. British Islands 

 generally. Length 12 lin. ; exp. 16 lin. 



Freezing of Boiled and Uncoiled Water. — 

 At Sheffield some of the ponds have been flooded 

 during the late frosts with hot water, to give them a 

 good surface for skating on. Can you or any of the 

 contributors to SciENCE-GossiP kindly tell me why 

 water which has been boiled, freezes sooner and 

 harder than unboiled? — Thomas JFinder. 



RECREATIONS IN FOSSIL BOTANY. 



The Fossil Flora of the Halifax Hard 

 Bed Coal. 



No. II. 



By James Spencer. 



I PURPOSE to give a series of short popular 

 sketches of the fossil plants found in the above 

 coal-bed in the Halifax district. Every student of geo- 

 logy is acquainted with the external appearances of the 

 common coal plants, but comparatively few know 

 anything about their internal anatomy. The literature 

 of the subject is not very extensive, and chiefly 

 confined to high-priced memoirs, for the most part 

 beyond the reach of the ordinary student. The chief 

 authorities on this subject in England are Professor 

 W. C. Williamson, F.R.S., of Owens College, Man- 

 chester, Mr. Carruthers and Mr. Binney. I can 

 speak from personal experience of the value of 

 Professor W. C. Williamson's Memoirs, published 

 in the Transactions of the Royal Society. They are 

 invaluable to the student of fossil botany, and too 

 much praise cannot be given to the learned Professor 

 for the scientific accuracy of his descriptions and the 

 remarkable fidelity of his drawings. My object in 

 writing these papers is not to attempt such full and 

 elaborate descriptions as the above writers have 

 done, but simply to give a brief and popular account 

 (the result of my own labours) of the fossil plants 

 found in the Halifax hard bed coal. 



Stigmaria. 



Stigmaria is one of the oldest known fossil plants, 

 and was formerly believed to have been a distinct 

 plant, but it is now well known to have been the root 

 of sigillaria and also of lepidodendron. Stigmaria is 

 one of the hardest and most durable of fossils, and 

 has withstood the action of denudation, even more 

 than the rocks in which they were originally enclosed, 

 and consequently its remains are found in the drifts, 

 clays, and rainwashings, abundantly distributed 

 through the carboniferous formation. I have occasion- 

 ally seen its water-worn fragments clustered together 

 in sandstone quarries, in such a position as to leave 

 little doubt that they had been fossilised, and after- 

 wards had been rolled about in the] waters of the 

 ancient carboniferous period, before being deposited 

 in the sand-bed. 



The natural home of the stigmaria is the seat-earth 

 found under nearly all coalbeds, but not exclusively 

 so, for the examination of these coal balls has shown 

 that stigmaria formed no inconsiderable proportion of 

 the coal itself. Its stems and rootlets penetrate the 

 substance of the coal balls in all directions, being by 

 far the most numerous fossils found in them ; in fact, 

 the rootlets are so numerous as to become the bete 

 noire of the student. They turn up in all sorts of places, 



