8 POPULAR SCIENCE. 



noticed; and here young physicians, led away by false in- 

 dications, began to administer copper as a cholera remedy, 

 but without success. Reasoning on the matter, the fact was 

 remembered that copper was not, under the ordinary circum- 

 stances of copper-smelting, volatile. The cholera preventive, 

 whatever it might be, must have been volatile must have 

 wrought its preventive agency through the air-passages, being 

 absorbed by the lungs. Explanation must be sought, not in 

 the copper itself, but in some collateral product or products. 

 These were sulphurous acid and arsenic ; could the preven- 

 tion of cholera be due to either of these ? 



Evidence on this point soon came to hand. It was found 

 that men engaged in certain other operations involving the 

 dispersion of sulphurous acid had also been free from cholera; 

 and accordingly a large amount of evidence was in favour of 

 the probability that sulphurous acid or its compounds would 

 be valuable agents in the treatment of cholera, or rather to 

 secure its prevention. All this accorded with previous know- 

 ledge as to this agent. The fact had long been known that 

 sulphurous acid absolutely prevented the fermentation of or- 

 dinarily fermentible things. In the year 1849 a considerable 

 amount of sugar-cane juice, charged in Barbadoes with sul- 

 phurous acid, was brought to this country uncharged, and its 

 full complement of sugar extracted. The Devonshire cider- 

 maker, wishing to produce sweet cider for the London market, 

 had long been in the habit of sulphuring his casks, as he called 

 the process, i.e. burning a sulphur-match inside the bung-hole 

 before turning in his yet unfermented cider. What he wished 

 to effect was thus actually effected the sjigar yet present, 

 but which under the ordinary march of fermentation would 

 have been changed to alcohol, remained sugar, the cider kept 

 sweet. Another illustration. Certain makers of fruit-pre- 

 serves in the City had discovered, whether by reasoning or 

 practice I know not, that by rinsing-out their preserve-vessels 

 with the soluble bisulphite of lime, fermentation of the pre- 



