98 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



zymotic and other germs whose presence is necessary to 

 the development of epidemic diseases. In one experiment 

 Frankland placed a solution of lithium chloride in a shallow 

 basin, acidulated it with hydrochloric acid, and dropped in 

 fragments of white marble. The effervescence carried off 

 the lithium particles, and colored strongly the flame of a 

 Bunsen burner held at the upper end of a paper tube live 

 inches in diameter and five feet long, held vertically above 

 the basin. A tin tube three inches wide and twelve feet 

 long was placed above this, and the burner held over it, with 

 the same result. The paper tube was then lengthened to 

 nine and a half feet, and the amount of lithium present in 

 the current seemed to be quite as great as before. The au- 

 thor concludes, 1st, that fresh sewage, through a properly 

 constructed sewer, is not likely to be attended by the sus- 

 pension of zymotic matters in the air of the sewer; 2d, that 

 if the sewage be allowed to stagnate, the evolution of gas 

 results, and the breaking of gas bubbles on the surface pro- 

 jects liquid particles into the air, and is a potent cause of 

 the suspension of zymotic particles in the air of the sew- 

 er; and, 3d, that it is of the greatest importance that foul 

 liquids should pass freely and quickly through sewers and 

 drain-pipes. 



Stoney has called attention to the erroneous conception 

 ordinarily entertained of a vacuum. lie assumes as prob- 

 able that in a cubic millimeter of any gas at the ordinary 

 temperature and pressure there is a " unit- eighteen " of 

 molecules (1,000,000,000,000,000,000), and consequently as- 

 serts that in every cubic millimeter of the best vacuums 

 of our air-pumps there remains a " unit -fifteen " of mole- 

 cules (1,000,000,000,000,000). Even in the so-called Spren- 

 gel vacuum, as indicated by one -tenth of a millimeter of 

 mercury on the gauge, there is a " unit -fourteen" of mole- 

 cules (100,000,000,000,000), one hundred million million, in 

 every cubic millimeter. 



Wagner has modified his form of apparatus for determin- 

 ing the densities of gases by their times of effusion through 

 minute openings in metal plates. In place of a straight cyl- 

 inder, closed at top by the plate and open at bottom, which 

 was plunged into a cylinder of water or mercury, he now 

 uses a long U tube, closed at one extremity by the perfo- 



