74 



POPULAR SOIETTCE ISTEWS. 



[Mat, 1888. 



by four of its affinities, while two other 0x3'- 

 gen atoms are held by one affinity each, the 

 remaining one being united with the monad 

 hj'drogen ; and it is important to notice that, 

 in the chemical reactions of sulphuric acid, 

 one half of the oxygen holds very different 

 relations from the other half, corresponding to 

 the different disposition of the valences or 

 affinities in the molecule. No higher quantiv- 

 alent than six is known to occur among the 

 elementary bodies. 



As it is impossible for anj' substance to 

 exist with an unsat- 

 isfied affinity, it will 

 be seen that no 

 monad element can 

 exist in a free state ; 

 and it is found bj- 

 experiment that 

 hydrogen gas, for 

 instance, does not 

 consist of a single 

 atom, H — , but of a 

 double atom, H — H, 

 where the two affini- 

 ties mutually' satisfy 

 each other. 



One of the most 

 remarkable circum- 

 stances in this con- 

 nection is the fact 

 that under different 

 circumstances the 

 same element may- 

 possess different 

 quanti valences. 

 Nitrogen, for in- 

 stance, in ammonia 

 gas, NHg, is a triad ; 

 but in ammonic 

 chloride, NH^Cl, it 



is a pentad, with the power of holding five 

 monads. Iron has two or four valences, 

 while sulphur has either two, four, or six, ac- 

 cording to the class of compounds of which it 

 is a part. 



It is not easy to explain these variations of 

 quantivalence, which correspond in some de- 

 gree, notably in the case of iron, to differences 

 in their chemical and physical relations, which 

 might almost indicate the compound nature 

 of these so-called elements. The relation 

 between the quantivalence and the atomic 

 weight is an important feature of the recently 

 discovered "periodic law" of the elements; 

 but, like many other phenomena, we must 

 content ourselves with observing the facts, 

 and wait for future investigations to furnish 

 a rational explanation of them. Whatever 

 raaj' be the reason, we know that every chem- 

 ical element is possessed of a certain number, 

 always either odd or even, of affinities, or 

 power of uniting with or neutralizing the 

 affinities of other atoms, and that no com- 

 pound can exist unless everj- affinitj' of each 

 atom is neutralized ; that is, the sum of all 

 the affinities in any molecule must be an even 

 number. These laws are based upon actual 

 experimental investigation, involving an im- 



mense amount of time and labor, and are 

 among the fundamental facts on which the 

 S3'8tem of modern chemical philosophy' is 

 founded. 



THE SNOW AS A BIRD-CATCHER. 

 The number of birds annuallj' destrojed bj' 

 the cold of winter is verj- large, especially when 

 the ground is covered with snow, so that they 

 cannot obtain food from the eartli. A Belgian 

 gamekeeper has recentl}- observed a new source 

 of danger to birds from a fall of damp, adhe- 



Fio. ]. 



sive snow. The accompanying spirited illus- j 

 tration is reproduced from La Nature, and 

 shows a partridge securelj- held bj' a large j 

 snowball, while a flock of ravens feast upon i 

 him at their leisure. 



when they return to the fields the snow ad- 

 heres to them ; and, as they drag it along, the 

 ball continually increases in size, in the same 

 waj' that the enormous snowballs which boj'S 

 sometimes amuse themselves by rolling up are 

 formed. After the ball becomes too heavy 

 for the poor bird to carry it farther, he must 

 either remain firmly anchored till destroyed by 

 the cold or birds of prej', or else, if he is fortu- 

 nate, he may be able to relieve himself of the 

 weight of snow and his tail-feathers at the 

 same time. Fig. 2 shows one of these snow- 

 balls with the tail- 

 feathers still at- 

 tached to it, which 

 is copied from a 

 photograph. The 

 mass of snow 

 weighed nearly ten 

 ounces. It is not 

 likelj' that such an 

 occurrence would 

 lake place except 

 under exception- 

 ably favorable con- 

 ditions, and we 

 presume that a 

 strong-winged wild 

 bird would have 

 less difficulty in 

 freeing itself from 

 ;i mass of snow 

 ihaii the semi-do- 

 Hiesticated animals 

 of a European 

 game-preserve ; but 

 it is a curious in- 

 stance of the many 

 perils to which wild 

 animals are subject, 

 and may possibly 

 be no small factor in the destruction of the 

 weaker varieties of birds. 



Fig. 2. 



It appears that during cold weather the birds 

 resort to the nearest stream or other body of 

 open water for the purpose of warming their 

 feet. Their long tail-feathers becoming wet, 



I [Special correspondence of the Popular Science Newt.] 



j BERLIN LETTER. 



The University catalogue for the coming half- 

 year announces a course of lectures by Professor 

 Di-. Krause, physician to the Emperor, on laryngos- 

 copy and rhinoscopy, as well as a free course on 

 tlie pathology and anatomy of the nose, throat, and 

 laiynx. Professor Helmholtz le.-'ves the LTniversity 

 at the close of the next term, to take charge of the 

 Imperial Physical and Technical Institute lately 

 established in Charlottenburg. Professor Momm- 

 sen closed his lectures last semester, and is soon 

 to make another trip to Rome for purposes of his- 

 torical research. Perhaps the long-delayed volume 

 on the Empire will be the result. 



The Gesellschafl fdr innere Medicin discussed in 

 its meeting last Tuesday the subject of the cancer 

 bacillus. Dr. Eniil Senger gave the results of his 

 bacteriological studies and experiments, proving 

 satisfactorily tliat Scheurlen's bacillus (alluded to 

 in my last letter) is not, after all, the germ of the 

 disease, but merely a harmless bacillus of common 

 occurrence in stagnant liquids and in the ground. 

 Dr. Senger inoculated two hundred and fifty ani- 

 mals — mice, rabbits, dogs — with cancerous matter 

 obtained from hospital patients, with no efftct. 



