40 



KNOW^LEDGE ♦ 



[July 20, 1883. 



According to these notions tinning copper vessels is not 

 only unnecessary, but is a source of danger, as it is common 

 to mix lead with the tin, partly because it is a much 

 cheaper metal, and perhaps, still more, because it facili- 

 tates the process. Many of the disasters attributed to 

 copper are now thought more likely to have been caused 

 by the tinning. An unclean copper vessel is pronounced 

 less dangerous than that one tinned with an alloy contain- 

 ing 10 per cent, of lead, and from 30 to 40 per cent, is 

 found to be a common proportion. The chances of lead 

 getting into the system are very great. The mischievous 

 metal lurks in sardines, tunny, and lobster, as well as in 

 the vegetables sold in tins. It is also to be found in shining 

 wall-papers, certain table-cloths, the glazing of earthenware, 

 and in a swarm of cosmetics. 



In India, it is customary for Europeans to have all their 

 cooking done in copper vessels, which are retinned every 

 few weeks. In the army some precautions are taken to 

 prevent the employment of a lead alloy in this process, but 

 ordinary poisons are easily checked. When some of the 

 so-called tinning is worn ofl' the copper, the lead is more 

 likely to be acted upon, and it is not improbable that some 

 supposed copper poisonings have beiii ellected by the lead. 

 We should be glad if our medical readers in India would 

 look into this question, and let us know the result. 



Small doses of copper salts are supposed to e.xert a pre- 

 servative action against typhoid fevers and some other com- 

 plaints. Workers in copper and players upon copper and 

 brass instruments are said to liave escaped from typhoid 

 poisoning better than other folks. Compared with the 

 whole population, they are a very small class ; there may 

 be other things besides their contact with a particular 

 metal that may help to secure their immunity. The ques- 

 tion demands further inquiry. 



THE FISHERIES EXHIBITION. 



By John Ernest Ady. 



III. 



IN that most delightful toaside resort in the Isle of Weight 

 called Freshwater there is a liay adjoining the little hotel 

 village known as Scratchell's LSay. The escarpment of the 

 chalk cliffs, which descends abruptly for several feet to the 

 level of the sea, shows in a most remarkable manner layer 

 after layer of chalk, alternating with linear bands of flints. 

 We have already solved the problem of the origin of the 

 chalk with the assistance of the microscope, but how about 

 the flint 1 It has been supposed that the flint derived its 

 existence from the tests of !>lUceous organisms which 

 abounded in the Cretaceous .seas, and which have been dis- 

 solved and redeposited in that new and obscure shape. W^e 

 pointed out before* that the tests of Foraini)tifera undergo 

 profound changes at great dnprhs. which ri^sult in the for- 

 mation of a fine " red clay " (a silicate of iron and alumina) 

 almost free from any traces of organised remains. \Vh may 

 now draw attention to the fact that in certain localities, 

 e.q. the Gulf of Mexico, in comparatively shallow watei 

 (100 to 300 fathoms), the calcareous shells of the 

 Foraminifera are subject to other changes, whereby 

 the chambers of their tests become filled with a 

 green material (also a silicate of iron and alumina), whilst 

 the calcareous walls gradually disintegrate and finally 

 dissolve, leaving behind the so-called "green sand" com- 

 po5ed of a mass of exquisite casts or pseudomorphs of the 

 shell chambers ; these finally break down and crumble 



* Vt su% ra, p. ?, 



away into a formless paste, the vestiges of former anima- 

 tion. Evidences of the organic origin of vast azoic for- 

 mations have thus been elucidated by the recent researches 

 of the deep sea explorations, and suggested to the mind of 

 the late Sir Wyville Thomson that many of the most 

 ancient (Cambrian and pre Cambrian) rocks, such as the 

 highly-metamorphosed ^slates, itc, may possibly have been 

 derived from foraminiferal and other remains. Whilst 

 noting these phenomena, Huxley* observes that the words 

 of Linn;eu3 may be literally true when he says : — 



" Petrefacta non a calce, seel calx a petrefactis. Sio lapides ab 

 animalibus, iiec vice versil. Sic rupes saxei non prima'vi, Bed 

 temporis lilioe." 



And he adds : — 



"And there may be no part of the common rocka, which enter into 

 the earth's crust, which has not passed through a living organism 

 at one time or another." 



But apart from the silent flints and clays, there are large 

 zones of the crust of the earth which testify aloud to the 

 former existence of myriads of lovely organisms which 

 resemble the Foraminifera in many things, but are possessed 

 of siliceous instead of calcareous tests. These Jiadiotaria 

 form great masses of rock in the Barbadoes. Fig. G is a 



Fig. 0. — PoLVLY.sTi.NA, " Barbadoea earth." Tertiary deposits, 

 Springfield, Barbadoes. x 300 diameters. (Ori^jinal.) 



drawing, magnified 300 diameters, of some of these 

 beautiful skeletons. They are called Fo/yci/stina, and may 

 be readily obtained for examination by the following 

 method : — 



Procure a small piece of the friable rock known as " Barbadoes 

 earth," put it into a large test-tube, and add equivalent bulks, each 

 of water and washing soda ; boil for about one hour. The upper 

 pellicle must now be poured off, fresh water and washing aodsk 

 added, and the boiling continued. These processes should be 

 repeated a third, and, if necessary, a fourth, fifth, and si.xth time, 

 until a fairly cleansed residue is left. The deposit thus obtained 

 may he calcined by the application of a strong heat if the objects 

 are to be examined by condensed reflected light under the micro- 

 scope ; but this further process is unnecessary if they are to be 

 mounted in a transparent medium, and observed with transmitted 

 light. Thug prejjared they will be freed from adhering extraneous 

 particles, and will present the wonderful beauty and symmetry 

 which has been outlined in Fig. 6. 



* " The Anatomy of Invertebrated Animals," p. 87. 



