1<> S. It. WUUams—New Tyj)i of Mercury Air- Purnp. 



I) and the tubes might very well be enameled inside, which 

 would give the same surface as glass, but the strength of iron 

 or steel. 



References. 



1 Geissler pump. Pogg. Ann., cxvii, rj. 610, 1862. 



2 Toepler pump, Dingl. Polyt. Journ.. clxiii, p. 426, 1862. 



3 Sprengel pump, Journ. Chem. Soc. (2), iii, p. 9, 186.5. 



4 Bunsen filter pump, Dingl. Polyt. Journ., cxcv, p. 34, 1870. 



5 Automatic Sprengel pump, this Journal (3), xx, p. 57, 1880 ; xxii, p. 



90, 1881. Wied. Ann., liii, p. 199, 1894. 



6 Review of pumps, Thompson, Journ. Soc. Arts, xxxvi, p. 20, 1887. 

 T Automatic Toepler pump, Wied. Ann., xliii, p. 624, 1891. 



8 Schulze-Berge pump, Wied. Ann., 1, p. 372, 1893. 



9 Gaede pump, Physik. Zeitschr. , vi, p. 758, 1905. > 



10 Kaufmann pump, Zeitschr. fur Instrumenten. , xxv, p. 129, 1905. 



11 Siemens-Schuckertwerke pump, Physik. Zeitschr., vi, p. 868, 1905. 



Physical Laboratory, Oberlin College, 

 Oberlin, Ohio, March, 1910. 



