POPULAR SCIENCE MONTHLY 



39.37 inches) in length, with an ex- 

 hausting ventilator placed in the middle 

 and with trains of a given gas-produc- 

 ing capacity passing on each track every 

 three minutes, he constructs a diagram 

 showing how the composition of the at- 

 mosphere of the tunnel varies at suc- 

 cessive points, and how, by an examina- 

 tion of the diagram thus made, it is 

 possible to discover the maximum vitia- 

 tion of the air, and consequently the 

 extent to which the conditions are satis- 

 fied. By one or two such constructions 

 any such problem may be solved to a 

 degree quite within the limits of prac- 

 tical work, and the effect of various 

 systems of ventilation compared. M. 

 Godfernaux discusses various systems of 

 ventilation, including those involving 

 the use of shafts, fan blowers and ex- 

 hausters, and air jets, and concludes 

 with a description of the Saccardo sys- 

 tem, in use in the Apennine tunnel of 

 the Bologna-Pistoia line, and to the St. 

 Gothard Tunnel. While all this inves- 

 tigation and discussion is of much value, 

 it certainly seems as if the true remedy 

 lies not so much in the removal of dele- 

 terious gases as in the absence of their 

 production. The substitution of electric 

 traction avoids altogether the fouling of 

 the air of tunnels and subways, and 

 electric locomotives are already used in 

 the Baltimore Tunnel in the United 

 States and elsewhere, and it seems as if 

 this remedy is the true one to be applied 

 in all cases. 



Liquid Air.— The following warn- 

 ing appears in The Engineering and 

 Mining Journal of March 3d: "The ad- 

 vertisements which are now appearing 

 in the papers all over the country of 

 companies which are to furnish liquid 

 air on a large scale must be accepted 

 with a great deal of caution. The pub- 

 lic mind has been very adroitly worked 

 up for the reception of these by lectures, 

 paragraphs in the press, and other 

 well-understood methods. Undoubtedly 

 liquid air possesses some valuable prop- 

 erties, and many striking experiments 

 can be performed with it. It is not by 

 any means certain yet that it can be 

 prepared, transported, and used econom- 

 ically on a commercial scale, or that the 

 difficulties in the way have been over- 

 come. We do not say that they may 

 not be overcome in the future; but to 



talk, as the advertisements do, of the 

 certainty that liquid air will soon large- 

 ly replace steam in furnishing motive 

 power is going entirely too far. Such 

 assertions have no present basis of fact 

 to warrant any one in making them. 

 The liquid-air people have a great deal 

 to do yet before they can establish their 

 claims or carry on business on a scale 

 that will warrant the organization of 

 ten-million-dollar companies. The ques- 

 tion of validity of patents is also quite 

 an open one. It is doubtful if there is 

 any valid patent on this subject." 



Taka-Diastase. — The following is 

 taken from an interesting article, by W. 

 E. Stone and H. E. Wright, in The Jour- 

 nal of the American Chemical Society: 

 " Taka-diastase is, so far as known, 

 somewhat similar to malt-diastase in its 

 chemical character, viz.: a highly ni- 

 trogenous substance, readily soluble in 

 water, and dependent upon certain con- 

 ditions of temperature for its maximum 

 activity. Its action is also affected by 

 alkalies and acids. It is produced as the 

 result of the growth of a species of 

 mold (Eurotinm oryzw, Ahlberg) upon 

 rice, maize, wheat bran, etc. For its 

 production, as at present practiced in 

 this country, wheat bran is steamed 

 and, after cooling, is sown with the 

 spores of the fungus. After twenty-four 

 hours in culture" rooms, at a tempera- 

 ture of about 25° C, the fungous growth 

 becomes visible. In forty or fifty hours 

 the content in diastatic material has 

 reached the maximum, and further 

 growth of the fungus is checked by cool- 

 ing. The material, now consisting of 

 the bran felted together with fungus 

 mycelium, is called ' taka-koji.' It 

 may be mixed with grain or starchy 

 materials in the same manner as malt 

 is used, and, like malt, will speedily 

 convert the starch into fermentable 

 sugars. An aqueous extract of the mass 

 may be used for a similar purpose. For 

 the preparation of a pure product, 

 which, however, is not necessary for or- 

 dinary industrial purposes, the aqueous 

 extract is concentrated by evaporation, 

 and on the addition of alcohol the dia- 

 static substance may be precipitated as 

 a yellowish powder, easily soluble in 

 water, of stable keeping qualities, and 

 possessed of an unusual power of con- 

 verting starch into sugar. The medi- 



