142 BULLETIN 173, U. S. NATIONAL MUSEUM 



and vertical tubes, filling the entire center of the shell. The shell 

 of the boiler is double, Avith the space betAveen serving as the water 

 reservoir, which is small compared to the tube surfaces. The exhaust, 

 let into the top of the stack, induces the draft through the boiler. 

 The grates are fixed and flat. No ashpit is provided. 



MISCELLANEOUS PUMPS 



CLOW ROTARY WATER PUMP, 1856 



U.S.N.M. no. 30865S ; original patent model ; transferred from the United States 

 Patent Office; not illustrated. 



This model was submitted with the application for the patent 

 issued to C. N. Clow, of Port Byron, N. Y., July 1, 1856, no. 15221. 



The model represents a cam pump in which two smooth elliptical 

 cams run in contact in a casing, which is roughly a horizontal figure- 

 eight in cross section. The cams are made to revolve together cor- 

 rectly by means of gear wheels on the outside of the casing on the 

 same shafts to which the cams are attached. The pitch line of the 

 gears correspond in shape to the ellipitical peripheries of the cams. 

 The pump is operated by a hand crank. 



EADS SAND PUMP, 1869 



U.S.N.M. no. 30S143; models; gift of the American Society of Civil Engineers; 

 not illustrated. 



Sand pumps or ejectors of the pattern of these models w^ere de- 

 signed and used under the direction of James B. Eads for removing 

 sand and gravel from the caissons employed in the construction of 

 the bridge over the Mississippi River at St. Louis, 1868-1874. 



The pump consists of a cylindrical casing into which water is 

 pumped under pressure and from which it can escape only through a 

 concentric internal pipe leading and discharging upward. The water 

 enters the lower end of the discharge pipe through a passage that 

 gives the water the shape of an annular jet. The jet creates a vac- 

 uum below it by which suction is created in a short intake pipe let 

 into the sand. Sand is thus drawn into the jet and carried upward 

 with the stream of w^ater. 



As used at St. Louis the pumps with 3-inch discharge pipes each 

 discharged 10 cubic yards of sand and gravel in an hour including 

 stones as large as 2^/2 inches in diameter. 



One model is sectioned, and both are mounted in an old little 

 exhibition case marked "Designed by James B. Eads, July 1st, 

 1869; St. Louis, Mo." 



