Februaby 1, 1897.] 



KNOWLEDGE. 



Practical Work in Phi/sics. By W. Gr. WoolU'cmbe, M.A., B So 

 P „\r X '',?"''°'' ^''''^' ) ^'- Must rated. The main feature 

 ut all Mr, -W ooUcombe 3 books ou practical pliysios for schools and 

 colleges 19 to provide a maximum of experimental illustration at a 

 mimmum ot outlay in the way of apparatus. In this book the 

 author deals with liglit and sound, and it is surprising how much real 

 work may be done, as here indicated, by the aid of a quite inexnensive 

 outht. It may be remarked, however, that the book itself, consideriu<r 

 dear'^^ ("inety-six pages), and probable cost of production, is yery 



Artistic Landscape Photography. By A. H. Wall. (Percy Lund 

 & Co.) Illustrated. There is plenty of information in this book on 

 the jiossibihties or the amalgamation, so to speak, of artistic feelin^ 

 tT„„ ''" P"rfl7^'"'l''^";^"^l,<'perations in photography; but it is more 

 than hkely that the author's ideal will never be realized, for, iud^in^ 

 trom the illustrations shown, whicli are admirable in their way ft is 

 not too much to say that most photographers can proiuce et.'ually 

 good pictures by the exercise of common sense in the choice of 

 subjects and discretion in the fclei'tion of points of view. However 

 the work may prove useful to those who desire to excel in the art ' 

 Til ?! "1 ^""'■"''- B.y J. W. Tutt. (George QUI & Sous.) Is. 

 schirM; T^i'tt*^ Wy class book for object lessons in clementarv 

 schoo s, Mr. 1 utt 5 little volume is well suited. At the beginning of 

 each lesson a list of specimens is given, the method ot teachiuT bein.' 

 much the same as that which is put forward in the late Dr. G.alirie's 

 First Book of Knowledge." Bla,-kboard notes for the teacher's U83 

 arc appended. 



Imects andSpUlers This book forms Part II. of the above work 

 Is.), about which we have nothing more to say, save that both books 

 are admirable m their way. 



.,hfr -ff'"^;;'""' J''"»Y.T Number, has made another innovation 

 which adds to the value of this excellent monthly re„ani of all that 

 IS useful to those who take an interest in photography. It has been 

 changed troin a twenty-four to a thirty-two page inaiazine, the larger 

 tM>e now used bemg much more hi harmony Vi'th th'fine en^raviifg" 

 trom an artistic point of view, and far more in,-iting to the^cnerai 

 reader than heretofore. femciai 



Messrs. Pastorelli & Rapkin have sent us a specimen of the 

 'Wilson dial raiugauge^ which automatically registers the rainfall, 

 midd et' °\=' '=]°^-l'-''l^'^ '^'^''-•- ,A bucket having a partition in the 

 middle is centred on a iionzontal axis, and the rain from the receiver 

 draining into the bucket, first one half and tlieu the other, cause, the 

 bucket to rock or t. t on its axis, and this movement through a vertical 



X'h Ind'o ''f't- Trl' "^'^-^ '" "^ '"™ communic'ates niot^Sn 

 to the hand, on the chal plate, winch register to the ^i^th of an inch 

 The device is very ingenious. The new patent vertical elf-rcistedng 



icrmometer is also worthy of notice. Of course, in the old Srrange^ 

 ment, where the thermometer was disposed horizontally the fluid 

 was liable to separate; but inconveniences arising from fic \ ca e 

 are obviously eliminated in this new form of instrument 



VV e are pleased to note the steady accession of the lat"est improve- 

 men m scientific apparatus to Messrs. Eoss's handsome cataL" cs 

 A 1 tlungs optical and photographic turned out by tliis firm m«- bJ 

 relied upon for excellence of performance, rational price and 

 durabdity. Among their latest additions are the - Eclipse '■ series of 

 microseopes, the chief virtue of which, it would appe^' s that tlmy 

 maintain absolute stability when used at any angle; tl e new mte nt 

 earre 't" T^/P'^-f.'y '^'^-g-'' i- -'-tii. dLinstiUi'n, ^ Ih 

 can be used for ordmary pro ection or vertically, the chan>.e of 

 position occupying only a few seconds ; and the paten Eoss-Hepwortl 



lei ■ 'Tnt'""? T^ ,"". ""^ t-*''"^^^ f^'^'"'-'^^ '" "»^ apparatus' The 



be „Vt ' 'ff "^ Pljotographic, are of worldwide i-epute. Amon.. 



the latter, the Ross-Zeiss and Eoss-Goerz auastigmatic, double and 



Ot course. It is impossible to do more than indicate a few out of the 

 many excellent things figured in the pages of the several , a aWues 

 and It will thei^efore suffice to add that this optical firm appare^nt'y 

 take pride m doing everything well connected therewith "^P"''"''* ^ 

 We have received from Messrs. John -VVheldon & Co. a very com- 



rtu::i hLS!^''^"^ "' '-''""'■'''''' ^"'^""^^ "^-^^ -'' -•■'"on 



%ttttvu, 



[The Editors do not hold themselves responsible for the opinions or 

 statement s of eorres pondenta.l 



UNDEEaEOUND CAVITIES AKD STREAMS IN IRELAND. 

 To the Editors of Knowledge. 



l,n!?„''T7^^' recent earthquake in England and the moving 

 bog in Kerry may call attention to the extent to which thf 



soil IS undermined with cavities in various parts of the 

 country. I spent a good part of my time for some years 

 in, I beheve, the moat extensive district of this kind in 

 Ireland, and though English readers are probably aware 

 of its existence, they may not be cognizant of its extent. 

 It stretches, I believe, almost the whole way from West- 

 port to Gort, thus crossing a great part of the counties 

 ot Mayo and Galway. I do not, however, know the end 

 ot It next tiort, and shall commence with the river at 

 iurloughmore or Claregalway, not far from Tuam. A 

 turlough IS a piece of land which forms a lake in winter- 

 er, at least, part of the winter— while it is often good grass 

 land in summer. But some of the Gal way turloughs fill 

 up with water and become dry again far too rapidly for the 

 surrounduig rainfall to account for. The water evidently 

 enters and leaves by subterranean channels, and its 

 presence or absence probably depends on the level of some 

 neighbouring lake or river. These turloughs are often of 

 considerable extent. But Turloughmore is a turlough no 

 longer, a channel having been cut through a hiU to allow 

 the water to run off. The underminmg of the soil shows 

 Itself in another shape. Not a drop of water runs through 

 that channel in summer. The river— a good trout stream 

 —sinks into the earth, and rises again, perhaps, two miles 

 below. But It does not sink at once. First, on a day that 

 i followed it in summer, down from Corofin, I heard a 

 little waterfall close to the bank, and found that a part of 

 the water was leaving the bed of the river and disappearing 

 through a crevice in the limestone rock. A little further 

 on I came to two or three little whirlpools caused by the 

 water sinking in the middle of the stream, and then 

 what was left seemed to run into a loose stone wall and 

 disappear. 



Going a little further west there is a little river in the 

 village of Headford. It rises a very short distance from 

 the VI lage and is evidently supplied by underground water, 

 but where it comes from I could not ascertain. The Black 

 Kiyer, from its vicinity, seems most probable, but I could 

 not find that its water was diminished. Possibly the 

 Meadford stream is a part of the Turloughmore Eiver or 

 else supplied by an intervening lake. Passing through 

 Headford we come to the Black Eiver. A considerable part 

 of this river smks a short distance below Shrule, and rises 

 again in two distinct streams at the distance of, perhaps 

 half a mile. Both streams run back to the original river' 

 the bed of which is never completely dry. Before reaching 

 Gong we reach another little stream at Douagh, or Cross 

 which exhibits the same phenomenon of partial sinking 

 and rising again ; but a short distance below the bridge over 

 this stream there is a rise of water which seems at kast as 

 likely to come from Lough Mask as from the upper waters 

 ot the stream itself. If it comes from Lough Mask, its 

 underground course can hardly be less than five miles 



The district between Lough Corrib and Lough Mask 

 especially about the village of Cong, is known to man^ 

 tourists for its underground waters. In summer not a 

 single drop of water travels the whole distance between 

 the two lakes above ground, yet the river which reaches 

 A Ir r." ^^y^' ^l^rough Lord Ardilaun's demesne of 

 Ashford, IS a large one. This river may be said to rise in 

 the village of Cong, the water being supplied by Lough 

 Mask ; but even below the village the water may be noticed 

 smking and rising again in the bed of the river. Less than 

 a mile above Cong is the Holy Well, which runs dry when 

 Lough Mask IS low ; and the course of the underground 

 water from this down to Cong can be plainly traced, the 

 rushing of the water below being sometimes audible 

 while at others it rises to the surface and forms a stream • 

 and m one place there is a second small lake, which being 



