SCIENTIFIC NEWS. 



[May 2nd, 1887. 



England, probably because heating beer to a temperature 

 which would destroy'all disease germs, would destroy the 

 pleasant flavour of the beer by flattening. Again, Pasteur 

 has fallen into a serious error of observation when he says : 

 " A brewer never prepares his own yeast the inter- 

 change of j'easts amongst brewers is a time-honoured cus- 

 tom which has been observed in all countries at all periods, 

 as far back as we can trace the history of brewing."* While 

 by no means denying that such a custom has been observed, 

 we maintain that it is based on a wrong theory and 

 need not be maintained in practice. Several brewers now, 

 knowing the value of their own particular growth of yeast, 

 cultivate it with great care, and would look with suspicion 

 on any strange growth introduced in their brewery. In one 

 case this continuous propagation has continued for thirty, 

 probably fifty years, and the yeast shows no sign of dete- 

 rioration. 



As one fact well established is worth any number of 

 hypotheses, we are content to leave this unexplained, but 

 we are of opinion, that with the increased use of the micro- 

 scope and its greater powers, much may be discovered re- 

 specting the varieties of alcoholic ferments. The theory has 

 already been started that a perfectly pure yeast {Saccharo- 

 myces cerevisicv) would give an insipid beer without 

 character. 



We would merely suggest in the foregoing remarks that 

 in spite of the incalculable value of the researches of Mon- 

 sieur Pasteur, to whom brewers will always owe a debt of 

 gratitude, there still remained, after the publication of his 

 work, a wide gulf between empiricism and pure science. 

 How far recent experiments have gone to bridge this over 

 remains to be considered on another occasion. 



(To be confiniied.) 



NOTES ON THE HEATING OF 

 BUILDINGS. 



No. 2. — Hot-Water Circulation (continued.) 



THE boilers already referred to are generally used with 

 circulating pipes,having internaldiametersof from two 

 to four inches, and the maximum temperature of the water in 

 them may be assumed not to exceed 180" Fah., or the water 

 in the boiler would be above the boiling-point (212? Fah.). 



Fig. 19. 

 Fig. 18. 



We may briefly describe this system as one in which the 

 volume of water in circulation is large, in which the surface 

 of piping which radiates heat to the building is also con- 



* " Studies in Fermentation," p. 186. 



siderable, and in which the temperature is moderate. 

 We now have to consider a system in which the volume of 

 water and the heating surface of the piping are both small, 

 and in which the temperature is comparatively high. The 



Fig. 20. 



system we refer to is generally known as Perkins's, and in 

 it the circulating pipes are less than one inch internal 

 diameter. It has also some other special features, to which 

 attention will be drawn. In the Perkins system there is no 



boiler such as we have before illustrated, but the water is 

 heated in a coil of wrought-iron piping running round the 

 walls of a furnace, and in contact with the hot fuel, so the 

 heating proceeds rapidly. The elevation of this furnace 



