10 



POPULAR SCIENCE XEWS. 



[January, 1SS9. 



exactly analogous to soda and potash. It', for i tioiis is opposed to each otlicr. The ImtteiHy, 

 any reason, we were unable to separate the 

 strongly alkaline ammonia into its two neu- 

 tral gaseous constituents, its compound nature 

 would not be indicated by any of its chemical 

 characteristics any more than is the case \\ith 

 the supposed elementary alkalies mentioned 

 alxtye. 



Two more dissimilar substances than nitro- 

 gen and phosphorous could hardly be imag- 

 ined, yet the inert incombustible gas is, chem- 

 ically speaking, a first cousin to the poisonous 

 wax-like solid which takes fire with the slight- 

 est friction, for their chemical reactions and the 

 compounds they form with other elements 

 are yery much alike. Oxygen and sulpinir 

 is another example of this strange relationship. 



All the abo\e examples are of the simplest 

 and most familiar kind, and are taught among 

 the first rudiments of chemistry ; and yet a 

 rational explanation of them is still wanting. 

 The atomic theor\ has been deyised to ex- 



place, but who can say what chemical combi- 

 nation really is .'' Again, we find three difterent 

 and and distinct solid bodies, charcoal, graph- 

 ite and diamond. The chemist can find but 

 one chemical substance, carbon, in them all, 

 and nnist content himself with calling them 

 allotropic forms. In the study of organic 

 chemistry we find hundreds of cases where 

 two or more substances, varying widely in 

 their physical properties, have exactly the 

 same composition, and the most learned 

 chemist in the world can do no more than to 

 attempt to explain the fact by an unproved 

 theory. 



The behavior of alloys, or mixtures of met- 

 als, is in many ways very remarkable. Bis- 

 nuith, lead, and tin when melted together 

 form an allov which fuses below the boiling 

 point of water, although separately the most 

 fusible of the metals, tin, requires a tempera- 

 ture of nearly 450° F. before it liquifies. 

 Platinum is one of the most infusible of met- 

 als, but if heated 

 w ith gold an alloy 

 is formed, which is 

 r e a d i 1 y w o r k e il 

 with the heat of ,1 

 blowpipe. 



Ammonia is a 

 perfectly colorless 

 gas, and sulphate 

 of copper in solu- 

 tion has but a feeble 

 tinge of blue, but 

 bring the two to- 

 gether and a most 

 magnificent blue 

 substance is formed. 

 A similar color is 

 obtained when the 

 pale yellowish fer- 

 rocyanide of potas- 

 sium is added to 

 the yellowish 



brown chloride of iron ; or, if we use the sul- 

 phocyanide, a blood-red color is produced. 



Glycerine is one of the most stable and in- 

 offensive of bodies, but add to it a little nitro- 

 gen and oxygen, both non-explosive in them- 

 selves, and we obtain the terrible nitro-glycer- 

 ine which explodes almost at a touch. In 

 gun-cotton we have the same (juality con- 

 ferred upon a harmless and useful fibre ; but 

 if we add the mysterious elements to a sub- 

 stance known as benzol, we obtain a jjrfxluct 

 which will not exjjlode, but possesses a pow- 

 erful odor of bitter almonds. 



Two more inoffensive, harmless, iuacti\e 

 elements than nitrogen and carbon could not 

 be found, but submit them to the mysterious 

 process of chemical combination, and we ha\e 

 cyanogen, one of the most deadly poisons 



known. If we combine nitrogen with hydro- and reproduction are the basis of all the ac- 

 gen, we form the ]5ungent annnonia gas, tions of li\ ing animals, but there are certain I 

 \vhich is in every respect a powerful alkali cases wiiere the exercise of tiuse two Time- i other (Fij;'. 2) shows a 



Kin. ■• 



for instance, is brilliantly colored, so that it 

 may be a conspicuous and attractive object to 

 its mate. Tbt: firefly lights liis •' pale, inef- 

 fectual fires" i'or the same reason. But this 

 \'ery conspicuousness would render them an 

 easy pre\' to birds and other animals ^\ hich 

 feed upon them, and tiiere must he some 

 means by which they can conceal tiiemselves 

 from their enemies, or the whole race would 

 soon be exterminated. 



To protect themselves from such attacks 

 we find that many insects w hen al rest w ith 

 their wings closed, have a maivellous resem- 

 blance to lea\es, branches, sticks, and other 

 inanimate objects. Xearh all our connnon 

 butterflies are less brillianth colored on the 

 lower side of their wings which alone is visi- 

 ble when at rest. 



There is a very common form of midsum- 

 mer locust which, when its wings are closed, 

 is almost exacth' the color of the dust of the 



road where it is 

 lound, but as soon 

 as it takes flight 

 its bright colored 

 \vings render it a 

 conspicuous object. 

 When it drops to 

 he ground it seems 

 to suddenU' vanish 

 and become a part 

 of the earth it so 

 closely resembles, 

 and sharj) eyes are 

 necessary to discox- 

 er its whereabouts. 

 We copy from 

 La yVa/«/rc two en- 

 gravings, one (Fig. 

 i) showing the cat- 

 erpillar of the elder- 

 moth ( llropetrix 

 sa/itb/icai-ta) , and 



plain a part of them, and serves the purpose 1 the remarkable resemblance which it has to the 



most excellently, but vet the existence of twigs of the bush on which it feeds. The 



atoms cannot be pro\ed, and e\ en if it could 



there would still remain many questions to be 



answered and phenomena to be explained. 



We need not despair however of the solution 



of the problems at some future time. Many 



patient investigators arc at work upon them, 



and if the progress of chemistry in the past is 



an}' indication of its advance in the futiue, it 



will not be many years before our conceptions 



of the nature and action of matter will he 



much clearer than at present. 



THE PROTECTIVE MIMICRY 

 INSECTS. 



OF 



;\s ex])laincd in Proiessor Stoller's article 

 ast month, the functions of self-preserxation 



