FRAGMENTS OF SCIENCE. 



ous over the business. The coun- 

 tenance of the President glows with 

 satisfaction over the thought of all 

 the good he is doing. For our part, 

 we view the matter in a different 

 light. The money will, of course, 

 meet certain expenses of govern- 

 ment in Puerto Rico; but there is 

 reason to fear that it will do as 

 much to pauperize the island in one 

 direction as the restriction of its 

 trade will do in another. What the 

 Puerto Ricans want is not alms, but 



commercial liberty. The repay- 

 ment of this money will not stimu- 

 late their trade; it will not stimu- 

 late anything except their helpless- 

 ness. It is an open question wheth- 

 er they will suffer more by our pro- 

 tectionist greed or by our wishy- 

 washy sentimentality. Meantime 

 what are we to think of the party 

 system whose exigencies place us in 

 so ridiculous a position before the 

 world ? How long shall it abuse our 

 patience ? 



{fragments of jiktetuje 



Ventilation of Tunnels. — The ques- 

 tion of the ventilation of tunnels forms 

 the subject of a series of articles, by 

 M. Raymond Godfernaux, published re- 

 cently in he Genie Civil. The principal 

 sources of definite information, upon 

 which the discussion of M. Godfernaux 

 is based, are the reports of the commit- 

 tee on ventilation of tunnels of the 

 Metropolitan Railway of London, and 

 of the commission appointed by the 

 Italian Minister of Public Works to in- 

 vestigate the tunnels of the railways of 

 the department of the Adriatic. Al- 

 though the vitiation of the air in a tun- 

 nel may proceed from three sources — - 

 i. e., the lighting, the respiration of the 

 passengers, and the combustion of the 

 fuel in the engines — yet the two former 

 sources are insignificant compared with 

 the latter, which alone need be consid- 

 ered. The principal products of com- 

 bustion which are injurious are carbonic 

 acid, carbonic oxide, and sulphurous 

 acid. Of these it is found that the pro- 

 portion of carbonic oxide should not 

 exceed 0.01 per cent, which corresponds 

 to 0.13 per cent of carbonic acid in 

 excess of the normal proportion of 0.03 

 per cent and to 0.00027 per cent of sul- 

 phurous acid. In practice it is found 

 that if the total proportion of carbonic 

 acid be limited to 0.15 per cent the pro- 

 portions of the other gases will be well 

 within the comfort and danger limits. 

 This is much lower than is often at- 

 tained in crowded auditoriums, where 



the proportion of carbonic acid some- 

 times reaches 0.4 to 0.5 per cent, but in 

 such cases there is no carbonic oxide 

 produced, while in the case of tunnels 

 traversed by steam locomotives we may 

 assume that the carbonic oxide will be 

 about 1 to 13 of the carbonic acid, and 

 the sulphurous acid about 1 to 440. As- 

 suming a given limit of deterioration of 

 the air, it would be easy to devise a 

 system of ventilation if it were possible 

 to treat the tunnel as if it were a closed 

 room or controllable space. In prac- 

 tice, however, the conditions are pe- 

 culiar. The space to be ventilated is a 

 long, narrow passage, usually open only 

 at the ends, and traversed periodically 

 often almost continuously, by trains in 

 one or both directions, these trains emit- 

 ting the objectionable gases and also 

 disturbing the air currents best adapted 

 to proper ventilation. How best to rec- 

 oncile these conflicting conditions forms 

 the problem under consideration. Where 



' there are but few trains it has been 

 proposed to close the ends of the tunnel 

 by doors, and provide a fan exhaust or 

 pressure system, but this method is 

 obviously limited in its applications. 

 The practical conditions which must 

 be considered are those in which fre- 

 quent trains in opposite directions pass 

 through the tunnel, and these condi- 



I tions M. Godfernaux has analyzed 

 graphically in a very interesting man- 

 ner. Assuming a double-track tunnel 



I eight hundred metres (a metre contains 



