December 13, 1900] 



NATURE 



167 



The temperature 85° C. was probably chosen because it 

 may be relied upon with certainty to kill pathogenic organisms, 

 especially the .tubercle bacillus. We believe, however, that a 

 temperature of 65° C, acting for twenty minutes, is sufficient to 

 kill the tubercle bacillus, and that, therefore, pasteurised milk, 

 i.e., milk heated to 68° C. for twenty minutes, is quite safe, and 

 certainly its flavour is almost unaltered. We are aware, of 

 course, that some observers claim that tuberculous milk may 

 retain its infective properties after pasteurisation, but the work 

 of Theobald Smith seems to explain the contradictory results 

 which have been obtained. He found that tubercle bacilli sus- 

 pended in water, saline solution, bouillon or milk were de- 

 stroyed at 60° C. in 15 — 20 minntes. If, however, a pellicle 

 forms on the milk, then the tubercle bacilli in the pellicle seem 

 to be protected, and may survive an hour's heating at 60° C. 

 {/ourn. Exper. Med., iv, 2, p. 217). 



NEW SYNTHESES OF SOME D JURE WES. 



"VAT TRAUBE publishes in the present number of the Berichte 

 *_ • further details on the new syntheses of uric acid, xan- 

 thine and the methyl derivatives of the latter — theobromine, 

 theophylline and caffeine. The starting point is either cyan- 

 acetic acid or its ester. Cyanacetic acid and urea in presence of 

 phosphorus oxychloride form cyanacetyl urea, 

 NH2.CO.NH.CO.CH2CN. 

 Also cyanacetic ester and guanidine combine with the separa- 

 tion of alcohol, forming cyanacetyl guanidine, 



NHjC( :NH). NH. CO. CH,. CN. 

 The further treatment of these two compounds is similar. With 

 alkalis they are converted into cyclic (pyrimidine) compounds. 

 Cyanacetyl urea forms 4-amido-2 :6dioxypyrimidine, whilst 

 cyanacetyl guanidine gives 2 : 4-diamido-6-oxypyrimidine 

 NH— CO N— C.OH 



CH, 



HO.C CH 



CO 



II' II II 



NH— C:NH N— C.NH2 



4-amido 2 : 6-dioxypyrimidine. 



NH— CO N— C.OH 



II II II 



HN:C CH, or HjN.C CH 



II II 



NH— C:NH N=C.NH2 



2 : 4-diamido-6-oxypyrimidine. 

 They are then treated with nitrous acid, which replaces the 

 hydrogen of the methylene group by an " isonitroso " group, 

 and this group is then reduced to the " amido " group by 

 ammonium sulphide, yielding the following compounds : 

 NH— CO NH— CO 



I i II 



CO C.NH2 HN:C C.NH2 



I • I II 



NH— C.NH2 NH— C.NHj. 



Boiled with formic acid, the first is converted into a formyl 

 derivative and the second directly into guanine, 

 NH— CO NH— CO 



II II 



CO CNH.CHO HN:C C.NH\ 



N- 



-C— N 



CH 



NH— C.NH2 



If chloroformic ester is used in place of formic acid, the first 

 yields a urethane. Both formyl derivative and urethane form 

 sodium salts, which, when heated, yield the sodium compound 

 of xanthine, 



NH— CO NH— CO 



II II 



CO CNNaCHO CO C.NNaCOOC.Hs 



I II I II 



NH— C.NH2 NH— C.NH2 



and that of uric acid respectively. 



NH— CO 



CO CNNa 



I II > 



NH— C— N ^ 

 Sodium xanthine 



CH 



NH— CO 



CO C.NNas 



NH— C.NH/ 



Sodium urate 



NO. 1624, VOL. 63] 



CO 



Guanine may be readily converted by Fischer and Strecker's 

 method into xanthine, and by methylation into theobromine 

 and caffeine, whereas by using methyl urea in the formation of 

 cyanacetyl urea in the first method, or by methylating the formyl 

 compound, theobromine, theophylline, caffeine and the corre- 

 sponding uric acids may be produced. A patent has been taken- 

 out by the discoverer for these processes. 



ARTIFICIAL RAIN.^ 



"T^HE question perpetually arises in the popular mind as to 

 whether man cannot produce rain or drought according as 

 his needs may dictate. The possibility of doing this is never 

 questioned by barbarians, who have their professional rain 

 makers and great medicine men, and superstitiously attribute 

 to them all power over nature. In some parts of the Christian 

 world it has been believed that man could bring about rain or 

 drought, not by his own power, but by intercession with the 

 Creator, who would, perhaps, work a miracle on his behalf. 

 During the past thousand years miracles have been confessedly 

 rare, and some consider it almost impious for a man to dare to 

 interfere with the operations of nature on a large scale ; some 

 even refuse to be doctored for disease. 



The recognition of the truths revealed by modern science has 

 made it evident that man can affect the weather only by under- 

 standing and making use of the laws of nature. He must do 

 it in a natural or scientific way, not through any supernatural 

 power or in any miraculous way. In fact, those who have a 

 very imperfect knowledge of the laws of nature, if any at all, 

 are often inclined to believe that there really must be some 

 process known to science, or still to be discovered, by which 

 man can bring abundant rain from the clouds when and where 

 he needs it. They point to the popular belief that rain follows 

 great battles, as proving that there is some way by which to 

 affect the clouds — it may be through the noise of the battle, 

 or it may be the burning of the gunpowder, or it may be a pos- 

 sible electric disturbance. They point to the reputed influence 

 of lightning rods, which are supposed to draw the lightning 

 from the skies and prevent the formation of hail. 



In these and other matters there is abundant room for self- 

 deception. It would be a great mistake to conclude that any 

 battle by reason of its noise, or heat, or gunpowder has had 

 any effect in the way of producing rain, or that the lightning 

 rods have had any effect in producing or preventing hail. The 

 statistics that are supposed to substantiate such conclusions do 

 not really prove anything of the kind, and yet many are deceived 

 by them because in reasoning upon the phenomena of nature 

 they forget to apply the simplest laws of logic, and are carried 

 away by emotions or preconceived opinions or the plausible sug- 

 gestions of others. This is not at all singular, for the history oi 

 man's progress in knowledge is the history of a long series of 

 mistakes covering thousands and tens of thousands of years. 

 All have to learn by bitter experience, and if science seems to 

 have made rapid progress during the past century, that should 

 not blind our eyes to the fact that errors may still prevail among 

 the professional men of science as well as the rest of mankind. 



In the special matter of the artificial formation of rain we 

 heartily endorse the statement that if it is in any way possible 

 to bring this about we must labour to discover it ; in fact, we 

 eventually shall discover the way, if there be one, but thus far 

 nothing has been accomplished to justify us in believing that 

 feasible methods exist or are likely to exist. Various methods 

 have had their advocates both in Europe and America, and the 

 citizens of the United States, with a nervous energy that is 

 greatly to be admired, have given a full and fair trial, at great 

 expense, to several methods advocated by men of imperious 

 natures that would brook no denial short of nature's own ex- 

 perimental demonstration of their errors. Thus the rain-making 

 by explosives was most thoroughly tested by order of 

 Congress at an expense to the public of many thousands of 

 dollars, and the results have been discussed sufficiently, both in 

 public and private, to show that nothing in the way of rain, and 

 probably nothing in the way of cloud or mist, was produced. 

 One of the first experimental trials was made quite near 

 Washington, D. C, at night-time, November 2-3, 1892, when 

 a series of clouds with showers were passing over the neighbour- 

 ing country, and these continued right along for several hours 



1 Abridged from a contribulion by Prof. Cleveland Abbe to the U.S. 

 Monthly Weather Reviciv. 



