YI BULLETIN 173, U. S. NATIONAL MUSEUIVI 



Facing page 



35. Hot-air engines 175 



(1) Ericsson hot-air engine, 1855. 



(2) Rider hot-air engine, 1871. 



36. Ericsson hot-air pumping engine, 1906 182 



37. Refrigerating machines 183 



(1) Audiffren refrigerating machine,1913. 



(2) Frost-Maker domestic refrigerating unit, c. 1914. 



