January 13, 1893.] 



SCIENCE. 



23 



and to canning and evaporating. The vegetable kingdom is every- 

 where responsive to the needs of man. 



5. Theve u a corresponding evolution in the 7iortietdturi.it. The 

 rapidity with which education and general intelligence have 

 spread in recent years is patent to every one. The rural classes 

 have risen with the rest, but among the agricultural pursuits 

 horticulture has probably shown the greatest advance in this re- 

 spect. The horticulturist grows a great variety of products, 

 many of which are perishable, and all of which demand expedi- 

 tion, neatness, and care in marketing. And these many and 

 various crops bring in a multitude of perplexities which not only 

 demand a ready knowledge for their control, but which are im- 

 portant educators in themselves. The horticulturist lives nearer 

 the markets and the villages than the general farmer, as a rule, 

 and he is more in touch with the world. Downing rejoiced in 

 1853 that there were "at least a dozen societies in different parts 

 of the Union devoted to the improvement of gardening, and to the 

 dissemination of information on the subject." Since that time a 

 dozen national horticultural societies of various kinds have come 

 into prosperous existence, and there are over fifty societies repre- 

 senting States, provinces, or important geographical districts, 

 while the number of minor societies runs into the hundreds. Over 

 fifty States, Territories, and Provinces have established agricul- 

 tural schools and experiment stations, all supported by popular 

 sentiment. The derision of "book farming" is well nigh forgotten. 

 Subjects which a few years ago were thought to be "theoretical" 

 and iiTelevant are now matters of common conversation. In 

 short, a new type of man is coming onto the farms. This uplift 

 in the common understanding of the science of cultivation, and 

 of the methods of crossing and of skilful selection, is exerting a 

 powerful accelerating influence upon the variation of cultivated 

 plants. But the most important and abiding evolution is that of 

 the man himself; and I expect that the rising intellectual status 

 will ultimately lead people to the farm rather than away from it. 

 We are just now living in a time of conspicuous artificialism ; but 

 the farm must be tilled and it must he inviting. When agricul- 

 ture cannot pay, something is wrong with the times. 



These, then, are the chief lines of progress in horticulture, and 

 they are all still operative and capable of indefinite growth. The 

 achievement of a generation has been phenomenal. The prospect 

 is inspiring to both the cultivator and the student. 



THE IMPORTANCE OF " NEXT-TO-NOTHING " IN CHEM- 

 ISTRY. 



BY W. H PENDLEBURT, M.A. (OXON), SCIENCE LECTURER OF DOVER 

 COLLEGE, ENGLAND. 



In the year 1888 the President of the British Association for 

 the Advancement of Science took for the subject of his inaugur- 

 al address " The Importance of ' Next-to Nothing.' " As a mat- 

 ter of course. Sir Frederick Bramwell treated his subject with 

 his usual wit and ability, and pointed out the influence of small 

 things on the advancement of his particular branch of science — 

 engineering. It might, however, be well to carry the idea still 

 further and to collect together, as far as is possible in a short pa 

 per, the facts that have come to light showing the influence of 

 traces of a foreign substance upon chemical change. Some of the 

 facts are almost paradoxical. Take the case of an ordinary coal 

 fire, which was probably one of the first objects which aroused 

 the interest and curiosity of mankind and awakened the instinct 

 of scientific investigation. It is needless to refer to the erroneous 

 views held on the subject of combustion, but it may just be men- 

 tioned that the discovpry of oxygen seemed to settle the matter 

 and to establish on a firm basis the whole theory of combustion. 

 In the years 1887 and 1888' the experiments of Mr. H B. Baker 

 made it quite clear, however, that the presence of aqueous vapor 

 had a great deal more to do with combustion and hence the burn- 

 ing of an ordinary coal fire than we were aware of. He showed 

 that if oxygen be rendered perfectly dry, by leaving it for some 

 time in contact with phosphorus pentoxide, combustion is ren- 

 dered impossible in such gas. Carbon, sulphur, or phosphorus 



' Preceedings o( the Royal Society, vol 45, and Phil. Trans., 1889 



may be strongly heated in an atmosphei-e of perfectly dry oxygen 

 without taking fire, and, in fact, the sulphur and phosphorus may- 

 be distilled in it. The presence of a trace of moisture at once 

 brings about the cumbustion. The writer has seen Mr. Baker 

 distil phosphorus in an atmosphere of oxygen and then, whilst the 

 phosphorus was still melted, admit a bubble of oxygen which has 

 been standing over water and at once the phosphorus burst into 

 flame. Hence it is highly probable that the ordinary phenomena 

 of combustion could not take place in our atmosphere if there was 

 not aqueous vapor also present. This would furnish another 

 reason against the probability of the moon's being inhabited, as 

 owing to the absence of aqueous vapor fire would not be possible 

 there. 



The great influence of a trace of moisture in bringing about 

 chemical changes in which of itself it is not directly concerned, if 

 we may so express it, is evident from many other observations. 

 Wanklyn discovered that dry chlorine will not combine with dry 

 metallic sodium, but that a trace of moisture will start the reac- 

 tion. Dixon found that a mixture of carbon monoxide and dry 

 oxygen will not be exploded by the electric spark, but that the 

 presence of a trace of moisture will bring about a silent combina- 

 tion under the influence of the spark, whilst if the gases are moist, 

 the explosion will take place readily. 



Again, it has been recently observed that ethylene and oxygen, 

 when perfectly dry. do not explode when acted upon by the elec- 

 tric spark, but the presence of moisture acts in this ease as in the 

 former. 



Again, carbon dioxide is not absorbed by dry lime. Sulphur- 

 etted hydrogen in the dry condition does not tarnish dry silver. 

 Dry iodine does not decompose dry sulphuretted hydrogen. 



We may take another example of the influence of next-to-noth- 

 ing of an impurity in bringing about a change in which its in- 

 fluence had been till lately liitle regarded. The experiments of 

 Mr. V. H. Veley=, of Oxford University Museum, on the action of 

 nitric acid on various metals has conclusively shown that the vi- 

 olent action which nitric acid has upon many metals is due to the 

 presence of a trace of nitrous acid in the nitric. He has kept 

 spheres of copper in the strongest nitric acid (freed from the pres- 

 ence of nitrous acid) for some time without any reaction occur- 

 ring, but when once a trace of nitrous acid or of any nitrite was 

 added, the copper was at once dissolved. The same kind of re- 

 sult was observed when mercury, silver, or bismuth were ex- 

 changed for the copper. It was found that from 1 to 2 parts of 

 nitrous acid in 10,000 of the nitric were suSicient to set up the- 

 reaction. 



Mr. Cross found that juts fibre, when treated with sulphuric 

 acid, is simply hydrolysed. If, however, ordinary nitric acid, 

 containing a trace of nitrous acid, be allowed to act on the jute,, 

 a considerable amount of chemical action takes place, and amongst 

 other substances, like urea, which either prevents the formation 

 of nitrous acid or decomposes it as quickly as it is formed, the 

 action of nitric acid on jute is strictly comparable with that of 

 sulphuric acid, simple hydrolysis taking place. 



It; is highly probable that many of the changes in organic chem- 

 istry, generally ascribed to the action of niiric acid alone, are due 

 to the presence of traces of nitrous acid. 



It is well known that pure zinc will not dissolve in pure hydro- 

 chloric acid or pure sulphuric acid, but the presence of a trace of 

 a metallic salt sets up the reaction very readily. 



If we take another branch of chemistry — metallurgical chem- 

 istry — the immense importance of the presence or absence of a 

 trace of a foreign substance in a metal is readily seen, since it pro- 

 duces an immediate effect on the hardness or tenacity of the met- 

 al, and so may de:=troy its usefulness in commerce. Take th& 

 case of copper. Professor Roberts-Austen states in his Cantor 

 lectures that a cable made of the pure copper of to-day will carry 

 twice as many messages as a similar cable made of the less pure 

 copper of 35 years ago, when the importance of the purity of cop- 

 per was not so well understood, and he quotes a saying of Sir 

 Wm. Thomson's that the presence of yV V^'^ cent of bismuth 

 in the copper of a cable would entirely destroy its commercial 

 success by reducing its conductivity. Sir Hussey Vivian ba!> 

 = Philosophical Transactions, 1691. 



