♦ KNOV^^LEDGE 



{Aug. 28, 1885. 



our feet, it must have been at a very early geological 

 period, for these old volcanic ashes can be proved to 

 ■underlie, and tlierefore to be older than, all the other rocks 

 here visible. The qnartzite, -we know, is of great anti- 

 quity, but these rocks at Barnt Green must be still older, 

 for they underlie the qnartzite. Now, at Nuneaton and 

 iit the Wrekin, volcanic rocks are also found beneath the 

 4uartzite. Moreover, in Wales, in Channvood Forest, and 

 elsewhere, a great mass of 1h, 11, ,1 ',,,l,:,,i;. ,,,,,> :islu's, 

 lavas, &c. — are found to ii', i ( ratal 



and are assigned to a I'l' r ; ,,, i ,, hifli 



includes the oldest stratified r . . . . I' ,s I [ ';, ■,■ , 1,1 \ , imy 

 knowledge. 



Thus it seems that, peeping out in this little comer of 

 the Lickey at Barnt Green, we have a representative of 

 the earliest-formed series of rocks known upon the globe 

 — the great Pre-Cambrian Formation — which are everv- 

 where unfossiliferous. Above them, and constituting 

 the ridge cnlled the Lower Lickey, comes the Cambrian 

 M"""'"*" '■ '• M I'lrTK ^^ is probably between 300 and 

 ''" '""i-raably on the qnartzite are 



' ,' :iIiove them come the coal- 



^"' ' ' ' xtreme southerly termination 



of_ the .Suii- - ' ■ coal-field; next we get Per- 



mian rock , . ; , , fragments of the older beds 



beneath; ■.,: .■],.. Trias, or New Red Sand- 



stone, m «ln,-, j;,,,,'., i :rl,ble-bed we see a great con- 

 glomerate of (qnartzite pebbles, many of which were 

 undoubtedly derived from the ridge of the Lickey, or 

 its extension. 



For although this qnartzite of the Lickey is now only 

 exposed as a tiny range of hilLs, yet in "carboniferous 

 times it formed part of a land-barrier wliieh extended 

 /icross central England fr. .m tlio liills of Cliarnwood to the 

 Malvems. Of this , M ' , i ,i ,. i[,,rt.shill range, Dost- 

 hill, the Lickey, tl,. -: ! --,,, at Dudley Castle 



and the Wren's Nt>: ., ; ul:i', and the Lnnr'- 



mjTid hills of Shr-j i ;!■ . - i- ,! ii ,m1' fi-a^nnents which 

 owe their present po.sitiun to the CMmbinecf action of the 

 volcanic forces by which they have been upheaved, and 

 the forces of denudation by which thev have been laid 



bare. But vari.ms (h'c|i b.ii-iiif-; mr-r," f"Mci:i]lv t iiose 



in Leicester>l,i", , i.Ml 1„.t,;,,.,,,, i ,,;,.,,,,,..! ,| [^,,j„],„jl_ 

 have revealr.l . .■ ■. ■':•..! th.^,. i,ld 



rocks beneaK i,';,, -,iii,;r.' ::t n . ■•■■,•,1 a^iiii ami tlier 

 form the fluo, u[ uli the eountrybetweeu the Thames 

 Valley on the south, and a curved line joining the 

 Malvern with the Charnwood hills on the north. 



It IS an interesting task to search in tlie ii.wer strata— 

 the Permians and the Trias- f- i il,, r, l.of this old 

 land, which reared its head j; '.waters in 



which they were deposited. I i; ' ue leadina- 



to Northfield, two or three ,„ 1 . .. .:;. ,: the'Lickey, 

 there i.s a section of Permian brc,;cia.s from which quite a 

 .suite of Silurian fossils may be collected, showing that 

 Silurian rocks formed the margin of the sea in which the 

 Permian strata were laid down. 



If the geologist can devote a whole day to the examina- 

 tion of the Lickey, he may, instead o'f returning fi-om 

 Barnt Green station, walk along the western side of the 

 Lickey ridge back towards Rubery. At the northern 

 end of the ridge several fine boulders are to be seen lying 

 on the roadside or in the waste corners of fields. These 

 boulders are mostly blocks of rock which have been 

 transported from North Wales by ice during the last 

 Glacial Period. Such blocks lie thickly, too, over the 

 country round Northfield, where the " Great Stone Inn " 

 takes its name from the mass of Welsh felstone which 

 now res-ts near its door. 



FINAL OPERATIONS FOR THE 

 REMOVAL OF FLOOD ROCK. 



FLOOD Rock, a ledge of gneiss situated about one- 

 quarter of a mile from Hallet's Point, Astoria, L.I., 

 is one of the most formidable of the many obstructions 

 by which all the commerce passing through Hell Gate 

 has been menaced. This rock forms a very irregular 

 obtuse cone, onlj' a small portion of the apex of which 

 comes above water. This formation and its location in 

 the bend of the river almost in the centre of a swift 

 current at each change of the tide make it an object of 

 great dread to pilots. The work of removing this rock 

 was begun in 1875, and after unnecessary and costly 

 delays caused by the failure of Congress to appropriate 

 sufficient mni;. y fi'..iii y.ar to year the entire excavation 

 has been com], hi id. ;ill tlic drill-holes have been bored, 

 and all that remains to lie done is the charging of the 

 holes with explosives, removing the plant, and dredging 

 the broken rock after the firing. The total cost of the 

 improvement will be about 1,000,000 dols. 



The method pursued mav be briefly described, the 

 familiarity of our re ah r- witli the uialertakiTi- render- 

 ing a detailed account iiia-alli-l f^r. A >liafi wa> .sunk 

 at the highest point of il.e r..ek t.i a .lejih ..f .-i.xty feet 

 below water level, and from this shuit galleries were 

 extended parallel with and at right angles to the current. 

 These galleries are twenty-five feet between centres, and 

 extend under all the rock to be removed. It was not the 

 design to remove the rock as much as possible by means 

 of these tunnels — owing to the fact that it would be 

 cheaper to dredge the broken rock after the explosion — ■ 

 which were only expected to serve as passageways honey- 

 combing the rock and through which acce.ss could be had 

 to all parts in order to place the powder. Absolute 

 regularity in the spacing of the galleries could not be 

 maintained owing to inequalitj' in the texture and forma- 

 tion of the rock. The plan view in the accompanying 

 illustrations shows the present condition of the excavation, 

 and, being dravin to scale, it presents a good idea of the 

 magnitude of the work. 



Thus was formed an immense chamber, averaging 

 about 10 ft. from floor to ceiling, having a stone roof 

 averaging about 15 ft. in thickness, and supported by 467 

 rugged and massive columns. In this chamber, running 

 parallel with the East River, are twenty-four galleries, 

 the longest measuring 1,200 ft., and ruiininu'- at right 

 angles to the stream are forty-six galleries, tlie longest of 

 which is 625 ft. The area covered by the chamber is 

 about nine acres. Tlie aggregate length of the galleries 

 is 21,670 ft. 



The mining operations were not attended with unusual 

 risk either to the men or the wrrk ; the main danger 

 was from the flooding of the mine through the opening 

 of a fissure, or the meeting with a ri ck "keyed the 

 wrong way," which would ailuii' ik v. a in- in quantities 

 too great to be handled by tk. ; I -iires were 



frequently encountered, but f'lii ■■ , < f excessive 



size; the large holes were ]■'. ._ i -i-k \v ood, loose 

 filling, such as cement, k. _ ' ' il le because of the 



great pres.sure of watii -a i the square inch. 



To escape the drip]a;._ ; a cases the pour- 



ings, from the roof, auil to eu,.kle the visitor to walk 

 dry-shod through the small brooks running down some 

 of the galleries, he is, through the kindness of those in 

 charge of the work, encased in rubber from head to foot. 

 The north-eastern portion of the excavation, having 

 an area of about one acre, was tlirough rock very irre- 



