TRANSACTIONS OF THE SECTIONS. 5U 



The author remarks that there are at least ten substances found 

 whose extremes are the same as No. 1, thirty-three the same as No. 2, 

 and nineteen the same as No. 3. Of the others only a few have as 

 yet been discovered. The calculation of the specific gravity of those 

 in the gaseous form agrees with experiment in a manner which in- 

 duces the author to urge upon chemists the examination of the hypo* 

 thesis from which the graphical and symbolical results which he pro- 

 duced were derived. 



The extremes after the first are successively doubled, each making 

 exactly one volume, to which the middle atoms, within the parenthesis, 

 contrijjute nothing : this remarkable result, the author observes, is 

 confirmed in all cases determined by experiment. 



Experiments on Fermentation, with some general remarks. 

 By Dr. Uke. 



A dispute having taken place between some distillers in Ireland, and 

 officers of Excise, concerning the formation of alcohol in the vats or 

 tuns by spontaneous fermentation, without the presence of yeast, the 

 Commissioners of Excise thought fit to cause a series of experiments to 

 be made upon the subject, and they were placed under Dr. Ure's gene- 

 ral superintendence. An experiment made on the 6th of October, 1837, 

 and another experiment commenced on the 12th of October, prove 

 beyond all doubt, that much alcohol may be generated in grain worts, 

 without the addition of yeast, and that also at an early period ; but the 

 fermentation is never so active as with yeast, nor does it continue so 

 long, or proceed to nearly the same degree of attenuation. 



By employing a peculiar mash-tub, which he had devised. Dr. Ure 

 succeeded in raising the produce of spirit by this process to a perfect 

 accordance with the Excise tables. 



The next experiments were made with a view of determining at what 

 elevation of temperature the activity or efficiency of yeast would be 

 paralysed, and how far the attenuation of worts could be pushed within 

 six hours, which is the time limited by law for worts to be collected 

 into the tun, from the time of beginning to run from the coolers. 



It would appear from two experiments, that yeast to the amount of 

 5 per cent, is so powerfully affected by strong worts heated to 120°, 

 as to have its fermentative energy destroyed ; but that when yeast is 

 added to the amount of 10 per cent., the 5 parts of excess are not per- 

 manently decomposed, but have their activity merely suspended till the 

 saccharine liquid falls to a temperature compatible Avith fermentation. 



Yeast, according to Dr. Ure's observations, when viewed in a good 

 achromatic microscope, consists altogether of translucent spherical and 

 spheroidal particles, each of about the 6000th part of an inch in dia- 

 meter. When the beer in which they float is washed away with a little 

 water, they are seen to be colourless ; their yellowish tint, when they 

 are examined directly from the fermenting square or round of a porter- 

 brewery, being due to the infusion of the brown malt. The yeast of a 

 square newly set seems to consist of particles smaller than those of 



