Sept. 5, 1878] 



NATURE 



507 



fluence of strike in determining the lines of direction of the 

 principal physical features of a country, is recognised by most 

 geologists, but in few countries is the relation so distinct as in 

 Ireland. The author was led to pay attention to this subject 

 some years ago on reading Mr. J- ^' Campbell's paper on the 

 glaciation of Ireland, ^ in \\hich that gentleman assumes that the 

 south-west and north-east trend of some of the mountains of 

 Ireland, e.g., those of Donegal and Kerry, is due to the glacial 

 action of a huge ice-sheet passing over Ireland from the south- 

 west of Scotland. The author, after some years' examination, 

 has found, however, that in most cases the trend of the hills, and 

 course of rivers, &c., are determined by the strike alone, and 

 wished to place the facts he had noted before the section. 



1. Mountains. — The Donegal highlands trend to the south- 

 west along the line of strike of the ancient crystalline stratified 

 rocks. The basaltic plateau of Antrim follows in outline the wind- 

 ings of the outcrop of the underlying chalk, and consequently 

 the strike of the basalt itself upheaved with it. The Mourne 

 Mountains and Slieve Croob also coincide in direction with the 

 stratified rocks on their flanks, except where joints or faults have 

 given rise to minor lateral valleys, e.g., Carlingford Lough. The 

 same adherence to the line of strike is seen in the hills forming 

 the flanks of the Wicklow Mountains ; in the Kilkenny and 

 Tipperary coal-fields; the Comeragh and Knockmealdown Moun- 

 tains ; and is most remarkably shown in that series of flexured 

 carboniferous and old red sandstone rocks forming the hills of 

 Cork and the Mountains of Kerry, the axes of which stretch 

 from Dungarvan (co. Waterford) to Cape Clear, and Bantry 

 Bay. The Reeks of Kerry are good examples. Its influence is 

 again shown in the shaping of the high ground forming the 

 Munster coal-field, and finally in the mountainous district of 

 Connemara, although here in places obscured by the action of 

 faults. The Twelve Pins, Muilrea, the mountains flanking Kil- 

 lary Harbour, and the country northwards around Nephin 

 Mountain are striking examples. Toward the central plain the 

 isolated mountains of old red sandstone and Silurian rocks rising 

 through the carboniferous limestone, viz., the Slieve Bloom 

 Mountains, the Devil's Bit, and the Galtees, conform to the same 

 rule, the axis of strike and direction being parallel. 



2. Rivers. — In the south of Ireland especially many of the 

 rivers follow the windings of the strike. The Suir follows the 

 line of strike for eighty miles, only beginning to cross it about 

 ten miles from the sea. The Blackwater runs along the strike 

 for seventy miles of its course, crossing it for only sixteen miles. 

 The Lee is directed by the strike for fifty miles of its length, as 

 is also the Bandon River for the greater part of its course, 

 while the Shannon may be traced along the strike of the beds 

 for by far its greatest distance. 



3. Inland Lakes. — Most of the lakes are conformable to the 

 strike in their greater outlines, the smaller details being deter- 

 mined by the jointage. Of these may be mentioned Lough 

 Neagh, Loughs Corrib and Mask, Lough Erne — most notably — 

 Lough Allen, Lough Derg, and the far-famed Lakes of 

 Killamey. 



4. Sea Lochs, Bays, <2r=t-. — The majority of these may be 

 included — Lough Foyle, Belfast Lough, Strangford Lough, 

 Lough Larne. The most notable examples are those on the 

 south-west. Roaring Water Bay, Dunmanus Harbour, Bantry 

 Bay, Kenmare River, and Dingle Bay. Also the mouth of the 

 Shannon, Galway Bay, and Clew Bay. Farther north, the 

 principal bays and indentations along the line of coast stretching 

 from Broadhaven to Donegal; Killala Bay, Sligo Bay, and 

 Donegal Bay, have been excavated in their great outlines along 

 lines of strike. 



In conclusion, the author pointed out that nature had adopted 

 the least expensive method of working ; since it is always 

 easier to excavate along a line of strike than across the bedding. 

 Usually cleavage, or incipient cleavage, is induced along the line 

 of strike by the forces which upheaved the rocks, and denudation 

 is most early effected therefore in this direction. 



On the Correlation of Lines of Direction on the Globe, by Prof. 

 O'Reilly, M.R.I. A. — The theory of correlation of the great 

 lines of direction on the earth's surface had long been studied 

 and applied, especially in mining ; and had been generalised by 

 Elie de Beaumont, and applied by him to the correlation of 

 mountain chains with remarkable results, but his theory had 

 found but little favour with English geologists. The author 

 having been led to examine the question, based his system on 

 angular relations actually observable in certain rocks, and in these 

 * Quart. Jourti. Geol. Soc, London, Maj', 1872. 



he had found the angles 40° and 70° to bear a very important 

 part. He gave details tending to show the relation of those 

 angles to the main lines of direction on the surface of the globe, 

 taking as a base line the east coast of Madagascar. 



OnHullite, a hither to Undescribed Miner at from CarnmoneyHill, 

 Co. Antrim, with Analysis, by Edward T. Hardman, F.C.S. — 

 This mineral occurs in abundance at Cammoney Hill, near Bel- 

 fast, in the basalt forming the old neck of a miocene volcano. 

 It has never before been described or analysed, and has been 

 referred to on the Survey maps and in the Survey collections 

 as obsidian, doubtless from its black colour and waxy lustre. 

 In physical character it somewhat resembles the chlorophaeite of 

 Macculloch, but is entirely different in composition, which more 

 resembles that of delessite. From this, however, it differs 

 essentially in colour, hardness, and specific gravity, but it 

 appears to belong, on the whole, to the ferruginous chlorite 

 group. 



Physical Characters. — Colour, black; hardness, about 2; 

 lustre, waxy, but dull ; before blowpipe, with difficulty fusible 

 at edges to a black glass sometimes magnetic ; very slightly 

 affect«i by strong acids in the mass, but nearly entirely de- 

 composed when boiled in powder, in strong hydrochloric acid, 

 occurs filling and coating vesicular cavities in basalt of Cam- 

 money Hill, &c. 



Chemical Composition. 



Silica 39*43 



Alumina io'35 



Peroxide of iron ... ... ... 20*72 



Protoxide of iron 3*69 



Protoxide of manganese ... ... trace 



Lime ... ... ... ... 4*48 



Magnesia ... ... ... ... 7*47 



Water I3"6i 



Carbonic acid trace 



Formula- 



9977 

 -{CaMgFe")3 (AlFe"')4 Si^Oai -f 7H2O. 

 Specific gravity, I "76. 



SECTION D.— Biology. 

 Department of Zoology and Botany. 



On the Stipules of Spergularia marina, by Prof. Alexander 

 Dickson, M.D. — As is well known, certain genera of Caryo- 

 phyllacecE, of which Spergularia is one, are distinguished by the 

 presence of stipulary appendages. On examining lately the 

 stipules of Spergularia marina, I was struck with a peculiarity 

 presented by them, which, if observed at all by descriptive 

 botanists, has not received the attention it deserves on account 

 of its remarkable character. The stipules are free from the 

 petioles and wholly cellular in structure. From connation of 

 those of opposite leaves they form interpetiolar stipules with 

 more or less regularly, though slightly bifid, extremities. Lastly 

 (and this is the important point), these stipules are united to 

 each other round the backs of the petioles, so that a sheath is 

 formed completely surrounding the axis and the two leaf-bases. 

 This connation of stipules round the backs of the petioles is 

 very interesting as being a rare phenomenon. Cases are not 

 uncommon where the two stipules are connate on the inner side 

 of the leaf -base, constituting the so-called "axillary stipule," 

 e.g., Fotamogeton lucens, &c., or on the opposite side of the axis 

 from the leaf, e.g., Ficus elastica, Ricinus, Astragalus alpina, 

 &c., constituting the " oppositi foliar " stipule; but the only re- 

 ference to connation behind the leaf -base I can find is in the 

 case of certain Astragali, by St. Hilaire, in his Morphologic. In 

 those species of Astragalus which I have examined I have not 

 seen any one in which the stipules are actually connate in this 

 way; but in some, e.g., A. alopccuroides, the bases of the 

 stipules extend round the back till they meet — a condition just 

 short of connation. In Spergularia, as we have seen, we have 

 the interesting combination of the interpetiolar connation with 

 connation round the back of the leaf. In English Botany I 

 observe that the condition is fairly enough represented by the 

 artists, but, as I have already indicated, the inorphological 

 peculiarity does not seem to have impressed itself on the 

 botanical mind. 



Dr. Eayley Balfour remarked that a good deal of confusion 

 existed as to the application of the term stipule, and showed 

 that in some cases it was applied to structures of very different 



