July tst, i8§7.] 



SCIENTIFIC NE^A^S. 



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the generally accepted theory that the line between vege- 

 table and animal life is so extremely fine that its existence 

 becomes doubtful. Professor Tyndall has shown us that 

 not only yeast, but multitudes of other germs, are floating 

 in the atmosphere (although to the naked eye the air seems 

 quite clear), that this is especially the case in towns, and 

 that the presence of these micro-organisms has no doubt 

 given rise to the theory of spontaneous fermentation. 

 He, moreover, shows the affinity between the compara- 

 tively large germs of fermentation and the many germs 

 of human disease, research into which has since occupied 

 Dr. Koch and other biologists, but this is too vast a subject 

 for more than a passing allusion here. 



Applying his theoretical knowledge, a brewer knows that 



large scale through cotton wool, or to carry on large manu- 

 factories in such pure mountain air, as that in which Dr. 

 Tyndall tried his experiments. Antiseptics may, within 

 limits, be used to advantage, but whatever is used to kill 

 the smaller germs diminishes the vigour of the yeast. 



We are thus thrown back, for practical purposes, on 

 common-place customs. It has been known for generations 

 by all good dairy women, that to keep the vessels sweet it 

 is necessary to scald them with quite boiling water. With- 

 out knowing that lactic fermentation is the result of life, 

 and that this life is destroyed at the temperature of boiling 

 water, this practice has become firmly established. It is 

 also known that boiled milk keeps longer than raw, that the 

 scalded cream of the western counties is a more stable pro- 



CoPY OF Photograph uv MouxLiL.iir rici'kk^en iinc riii; i'aih tn hie Mui 



Taken by Mr. James Jackson, P.\ris 



AX EXPOSURE OF ONE HOUR. 



the change which takes place in his fermenting vessels is 

 the decomposition by a living organism of the maltose 

 sugar, and the formation of alcohol and carbon dioxide, 

 with a small quantity of subsidiary products of no value. 

 He examines with his microscope the form and growth 

 of the organism or yeast, and sees whether it is vigorous 

 and budding, or shrunk and withered. Should the latter be 

 the case, he knows it implies starvation, and that more food, 

 or more oxygen, is required. Sometimes, however, the yeast 

 cells are healthy, but are accompanied by germs of another 

 form. If these are minute dots, either single or in pairs, 

 forming the figure 8, he knows that they would set up a 

 lactic fermentation ; but if the foreign germs have the form 

 of minute rods, sour beer would be the result, for these 

 are the acetic germs of the vinegar maker. The chaplets 

 of dotted germs denoting ropy fermentation, we hope do 

 not enter modern breweries where cleanliness is studied. 



It is easy to discern between some varieties of yeast, e.g., 

 the Saccharomyces cerivisias and the favourite S. Pasto- 

 rianu^ of the Burton breweries. 



The great difficulty is to get rid oi these microscopical 

 mischiefs. Monsieur Pasteur boldly suggests either that 

 fermentation should be carried on at so low a temperature 

 as to require tons of ice and miles of underground cellars, 

 or that after fermentation had reached the necessary point, 

 the beer should be heated. To the first of these, the cost 

 of production is a fatal objection ; to the second the loss 

 of flavour by driving off the carbon dioxide is an insurmount- 

 able difficulty. Neither is it possible to filter the air on a 



duct than the raw cream of the other parts of England, and that 

 the butter made from scalded cream also keeps sweet longer. 



Following the same principle, brewers find that all fer- 

 menting and other vessels need constant and thorough 

 cleansing with boiling water, and this cleanliness is a more 

 formidable opponent to all disease in ferments than the 

 most elaborate apparatus yet suggested. 



But we must not forget, while acknowledging our debt 

 to old customs, that they were the result of empirical obser- 

 vation, not of scientific principles. In the words of Professor 

 Tyndall, " The brewer learnt from long experience the con- 

 ditions, not the reasons, of success It is the hidden 



enemies against which the physician and the brewer have 

 hitherto contended, that recent researches arc dragging into 

 the light of day, thus preparing the way for their final 

 extermination." 



Carbonic Acid in our Atmosphere. — It has been generally 

 supposed that the percentage of carbonic acid in town and 

 country air and in land and sea air would differ ; but in experi- 

 ments made by M. Blochmann, he has observed little difference, 

 and, according to this gentleman, it really appears that vegeta- 

 tion, putrefaction, and the smoke of chimneys, have but a slight 

 influence on the percentage of carbonic acid. There is, how- 

 ever, a little less in the air during daytime on land, and more in 

 foggy weather and with a dull sky than with a clear sky and a 

 fresh wind ; stormy winds have their effects according to local 

 peculiarities. M. Blochmann has been unable to determine any 

 law with regard to the influence of rain. Violent volcanic 

 eruptions, of course, affect the amount of carbonic acid 

 materially. 



