SCIENCE-GOSSIP. 



267 



(Menziesia pollfolia), the Mediterranean heath (Erica 

 mediterranea), and the large - flowered butterwort 

 (Pinguicula grandiflora) occur nowhere else in the 

 British Islands ; however, all these reappear again in 

 Southern Europe. Every one of them, too, is found 

 on the west coast. But besides these southern 

 plants, two species occur on the west coast of 

 Ireland, which, though unknown elsewhere in 

 Europe, have been found in North America. These 

 are Spisanther gemmipara and Sisyrhinchium anceps. 



All these facts of the geographical distribution of 

 animals and plants are of much greater importance 

 than it would at first sight appear. The southern 

 relationship of not only the few more remarkable 

 species which were mentioned, but that of the 

 whole Irish fauna and flora, points undoubtedly to 

 a former land connection of Ireland with the south. 

 Whether a direct land passage existed between the 

 south-west of Ireland and Spain, as the late Prof. 

 E. Forbes believed, or whether Ireland was con- 

 nected with France by way of the south-west of 

 England, are questions which have not as yet been 

 definitely settled. Ireland has also a good many 

 species in common with Scotland, so that it may be 



assumed that these, two countries were also con- 

 nected at no very distant geological period. The 

 soundings made in the Irish Sea have brought to 

 light the interesting fact that there is a deep hollow, 

 over one hundred miles long, which, at the time 

 when Ireland may have been connected with the 

 south-west of England in the south and Scotland in 

 the north, probably formed a fresh-water lake. 



These and many other attractive problems sug- 

 gest themselves to naturalists as a result of a study 

 of the fauna and flora, and they are of much help 

 to the geologist in mapping out the changes in the 

 physical geography which the British Islands have 

 undergone during the recent periods of geological 

 history. 



Ireland still offers a great field of study to the 

 zoologist and botanist. Many new discoveries and 

 additions to the fauna and flora have been made 

 known to the world in the columns of the " Irish 

 Naturalist," which should be consulted by all those 

 who wish to spend their summer holidays in 

 visiting the still unexplored regions of the west 

 coast. 



Science and Art Museum, Dublin; January, 1895. 



DENDRITES. 

 By John T. Carrington. 



Dendrite on Flint in 

 Mr. W. Gamble's collection 



T will be remembered by 

 readers of Science Gossip 

 that there was figured 

 (ante page 85), a group 

 of dendritic crystals, 

 observed by Mr. A. F. 

 Tait, in the pages of a 

 book. This subject has 

 evidently excited con- 

 siderable interest, as 

 manifested by the fre" 

 quent communications 

 which have been sent 

 to this magazine since Mr. Tait's notes appeared. 

 Recently Mr. W. Gamble of New Brompton, 

 Kent, kindly placed at my disposal for examina- 

 tion, a box containing a large number of specimens 

 of fractured flints found in the neighbourhood 

 of Chatham, showing various arborescent patterns 

 upon them, caused by dendritic crystallization of 

 some metal oxide, probably oxide of manganese or 

 peroxide of iron. Three of these examples I have 

 had figured as illustrations of the extremely 

 beautiful arborescence in flints which may be 

 found by those who have patience to look for such 

 specimens. 



Before quoting Mr. Gamble's notes on this sub- 

 ject, it may be well to recapitulate what has 

 previously been written about it. As far back as 

 1814 Maculloch communicated a paper to the Geo- 

 logical Society, which was printed in their " Transac- 

 tions " (vol. ii., page 516), on " Vegetable Remains 

 in Chalcedony," referring especially to the moss-like 

 groups in Mocha-stones, which were then, of course, 

 well understood, as indeed were they in 1763, for in 

 that year we find from " The New and Complete 

 Dictionary of Arts and Sciences, by a Society of 

 Gentlemen," that persons were warned not to think 

 the patterns were of plant origin in " Dendrachates," 

 which was a name used for "figured agats " or 

 " Mocoa stones," or " phassachates." Maculloch, 

 however, tried hard to prove these patterns were 

 fossilized mosses or sea-weeds. His paper was 

 carefully argued, and illustrated by drawings. 



Many metals, when held in solution in water which 

 percolates into fissures of rocks, stones or flints, are 

 slowly deposited as crystals, which partake of these 

 tree-like patterns. In most collections of minerals 

 such groups are shown, one of the most frequent 

 being copper. There are fine examples of the kind 

 in the Jermyn Street Museum, London, and also in 

 the Natural History Museum at South Kensington. 



