KNOWLEDGE 



[Au, 



18; 



acquire its natural firmness and pitchy colour. Previous 

 to every moult, the mealworm acquires a bloated appear- 

 ance, and becomes inactive for a time, lying on its side in 

 a curved position, and resenting all interference with 

 petulant twitchings of its form. 



These mealworms will attack bread, cakes, &c., as well 

 as uncooked cereals, and they have also been accused of 

 devouring corks. 



When we remember how many different species of 

 " corn-loving " beetles occur in our corn-stores, and how 

 excessively abundant some of them are, we are forced to 

 the conclusion that many must often be ground iip with 

 the flour, and that we, therefore, sometimes get our 

 bread adulterated with pulverised beetles, and uncon- 

 sciously become " insectarians " for the nonce. But " what 

 the eye docs not see, the heart does not grieve over," and 

 possibly we may not really be any the worse for this 

 slight admixture of animal matter with our farinaceous 

 diet, though there are not wanting those who have thought 

 otherwise. Many of these " corn-lovers " are Heteromera, 

 as we have seen, and to this section belongs also 

 the blister-beetle renowned in medicine, and 

 distant connection of our Tenehrios. Mor 

 Brazilian species of Tenehrio is known to eject from its 

 body a caustic secretion, and some other allied insects 

 cover themselves with a similar substance. Now if our 

 mealworms, &c., have properties at all analogous to those 

 •of Spanish Ply, this internal application of cantharides, 

 even in homoeopathic doses, might not, perhaps, be 

 altogether desirable. Some, too, have supposed the 

 -celebrated com-weevils to be prejudicial to health when 

 in a comminuted state. 



Flour is not the only article of food that is liable to 





adulteratio 



n this 



way. 



Curtis, 





n Insects," 



has the following uncomfortable and suggestive passag( 

 " I have known bushels of cocoa-nuts {i.e., of course 

 facao) which were every one worm-eaten and full of 

 maggots, with their webs, excrement, cast-off skins, 

 pup», and cocoons, all ground down to make chocolate, 

 flavoured, I suppose, with vanilla." 

 (Jo he continued.) 



E 



THE YOUNG ELECTRICIAN. 

 Bt W. Sungo. 



{Continued from p. 48.) 

 X. XCV. — The form of rubber referred to in the 

 preceding example is that pictured in Fig. 51, 



#^^.^ 



which consists of a pad, P, composed of a few layers of 

 silk, large enough to surround the glass tube upon which 

 the rubber is to be used. Along one edge of the pad a 

 strip of thin brass or other metal, M, is stitched, and in 



ire pierced a n 

 ng inserted an 

 ukl all turn in 



'Irs, the point of a pin 

 i.h liole. The point.-> 

 i.^s close to the surface 

 MS along it. A piece 

 to M ; the other end 

 I, or wherever else the 



Ex. XCVL— An. 

 a pith ball from t 

 Fig. 47, by means n 

 approach of an t 

 attraction of the pith-ball, 



liicli, coming into contact 

 with the glass, becomes similarlj' electrified, and is con- 

 sequently repelled. Although repelled by the glass, it 

 will be energetically attracted by an electrified stick of 

 sealing-wax. After contact with the wax, the electrifica- 

 tion of the ball will be reversed, repulsion will set in, 

 and the glass will next attract the pith-ball. 



INDUCTION. 



Pk. 4. — By induction is meant the electrification of a 

 body by the influence of another body already electrified, 

 near, but not in contact with it. 





F.g 52 



E\. XCVII.— In Fig 52 A B i-, a ghhS tube, of ^^hlch 

 the end A has been electrified and placed near the con- 

 ducting body C D, which may be the orthodox brass 

 cylinder ^ith rounded ends, although it may be con- 

 structed in a much less elaborate fashion. Take half a 

 sheet of foolscap jjafier, and make a rigid tube with it. 

 To do this, procure a large ruler, or other round rod, an 

 inch or more (two inches is a good size) in diameter, and 

 roll the paper round the rod once ; pull tight, and cover 

 the upper surface of the remainder of the paper with 

 floixr paste, glue, or preferably with gum. Then wind 

 the whole of the paper on to the rod or ruler, pulling it 

 as tight as possible. Bind up the paper with string, and 

 lay aside till the gum is drj', when the string may be 

 unwound, and a first-class rigid tube will result. Provide 

 the tube with rounded ends. A wooden ball (such as is 

 procurable at a toy-shop) cut in half will answer this 

 purpose very well, so also will a couple of tolerably round- 

 egg-shells. 



Or a solid wooden cylindor mnv be procured, the main 

 features being that tlir m'J, s sIimII 1,c parallel, free from 

 edges, ridges, or {xiiuts, ami tin- nuls rounded. 



The cylinder being iir.idupi'd, it requires a conducting 

 surface, which may be imparted by coating it with tin- 

 foil. This is easily done, tiu being a very soft and ductile 

 metal, aad tolerably porous. Before being applied, the 

 foil should be well smoothed, which may be done by 

 rubbing it with any round body, such as a chisel-handle. 

 This being done, and pieces of the requisite size and 

 shape being cut off, the cylinder may be coated by a good 

 application of flour paste, a little gentle pressure being 

 all that is necessary to ensure the adhesion of the foil to 

 the wood or paper (whichever may be employed). The 



