372 



KNOWLEDGE • 



[March -i, 1882. 



in inovinjr it about hIihII not be hindpred by other cilia 



imllin;; in wroii^ ilirci-tionH. 



Till- t<'n(li-iuv i>f miitlcr in motion to become rhythmical 

 is wpII known t<;> all physicists. Air readily vibrates in 

 musical pulsations ; the waterfall makes its musical chord, 

 and the pendulums (if adjacent clocks are said to conform 

 their beats. All such considerotions are very int/'restinj;, 

 and they enable us to find resemblances of analysis between 

 tiie action of our ciliated infusoria and a host of other 

 ihythmical and orderly processes. Our explanations, how- 

 ever, soon come to an end, and wonder cngulphs us where 

 actual knowled;.;e fails. 



In another paper we will endeavour to obtain some more 

 ideas of natural history and physiology from our hay 

 infusion. Now, we will only add that cilia are found in 

 all the vertebrate animals, and in most of the invertebrates, 

 though not in crabs, spiders, and insects. Man has them 

 in many places si)ringing from epithelium cells, in such 

 living membranes as those of the laryn.x, trachea, and 

 bronchial tubes. They do much in their situations to keep 

 back dirt particles, but their success is far from perfect. 

 Town ail-, especially foggy days, makes the human being 

 too much of a dirt-bin to be consistent with health. 



THE CRYSTAL PALACE ELECTRICAL 

 EXHIBITION. 



Fourth Notice. 



VERY pfreat progress has been made during the past 

 week in all departments, more especially in that 

 (if electric lighting. Siemens, Swan, Hawkes, Gerard, 

 .Jablochkofl", (.tc, are all at work. 



The Palace has never before looked so attractive, and 

 even the gallery, with its quota of light, is very pleasant, 

 lioth to the visitor and the exhibitor. One of the collec- 

 tions which visitors should not fail to inspect is that 

 in the north nave, exhibited by the War Office. The most 

 attractive feature of the exhibits is the destructive appa- 

 ratus, torpedoes, (tc, technically termed " mines," a name 

 which is perhaps more innocent or less startling to tender 

 nerves, than that by which they are more generally known. 



Tliey arc exhibited in various forms and sizes, but, of 

 course, none of them are charged. One, made to contain 

 100 lb. of gun-cotton, is suspended from the roof, and 

 represents the manner in which it would be moored so as 

 to float near the surface of the water. Mines, however, are 



generally of a larger size, and arc placed on the river-lied 

 or seu luiftom, where the depth do<-s not exceed CO feet 

 In deeper wat4'r they are suspended by a buoy (containing 

 the circuit-closing apparatus, to lie described further on) 

 at a depth of .'iO feet. Some of the specimens exhibiu-d 

 are constructed to hold a charge of .lOOlb. of gun-cotton, 

 which, on exploding, aut^jmatically or otherwise, %t the 

 above-mentioned depth, sends into the air a column of 

 water HO feet in diameter and 1 ."iO feet high. 



Fig. 1 illustrates what is known as the " circuit-closing 

 apparatus." S K' is a steel rod rigidly fixed at the Ixittom. 

 and weighted at the thin upper end, which is free. A small 

 collar of brass (K) is attached to the rod at aVxjut the middle 

 of its length. Round K is a ring of ebonite (E), to insu- 

 late another Vira.ss ring (B) from the rest of the apparatus. 

 The brass ring (F) is a portion of the framework, and is 

 metallically connected to the flat brass spring P. The 

 wire from one end of the battery (alx)ut four Leclanche 

 cells) on shore is connected to the brass ring B. When a 

 vessel strikes the buoy or mine, as the case may Vje, the 

 steel rod oscillates sufficiently to make contact between the 

 ring 1! and the spring P. The current will then pass fronv 

 B into P, and thence through the framework — the electrical 

 circuit being completed through the water and earth. So far, 

 however, no more damage is done than to ring a bell on 



0" 



G 

 I ft 







Fig. 2. 



shore. Fig. 2 shows how this is done. MM' arc exten- 

 sions (known as pole pieces) of the soft iron core of am 

 electro-magnet The current which is produced by the 

 impact of a vessel on the buoy passes through the electro- 

 magnet, and in consequence II and il' attract the piece of 

 soft iron, A A', which is pivottcd at C, so that both M and 

 M' tend to draw AA in the same direction. 1) is a pin on 

 AA', RR' is a lever, with the hammer, H, at one end, and 

 pivoted at C, so that when AA' is drawn away, D allows 

 H to fall, and strike the bell, L. This gives notice to the 

 officer of the approach of a vessel, which he may then blow- 

 up. The blowing-up, however, is very easily made auto- 

 matic. NN' (tig. 2) is a piece of brass, with a slit wide 

 enough to allow the hammer-lever in falling to enter and 

 make contact at O. This completes the electricad circuit for 

 firing the mine. Of course, all tliis is but the work of an 

 instant. 



The fuze is represented in fig. 3. B is the beechwood 

 cup, and W W are the extremities of a piece of line 



