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SCIENCE. 



[N. S. Vol. XVII. No. 423 



which becomes clearer as the matter is 

 further, examined, and the peculiar collat- 

 eral advantages of sixteen are appreciated. 

 To do this fully will require another paper, 

 but some of them may be mentioned in 

 the hope of eliciting comment and discus- 

 sion. 



The Drainage Problems of In-igation: C. 



G. Elliott, Washington, D. C. 



A new problem confronts the owners of 

 irrigated lands. The leakage from canals, 

 and over-irrigation by users of water, have 

 destroyed the productiveness of land by 

 producing saturation of soils in certain 

 localities, and resulting alkali conditions. 

 Well-directed drainage operations will re- 

 claim such lands and protect those which 

 are threatened with the evil. 



Second Law of Thermodynamics: J. BuR- 



KiTT Webb, Hoboken, N. J. 



Various attacks have been made on this 

 second law, and in a recent one by Jacob 

 T. Wainwright, of Chicago, of which I 

 shall not attempt a full criticism, there are 

 some peculiarities, two of which may be 

 worthy of remark. 



In the first place the writer seems igno- 

 rant of, or avoids, Rankine's work in this 

 direction, which, to my mind, contains the 

 best statement and proof of the law, in no 

 way touched by his remarks. 



The proof is like a nutritious nut— crack 

 the shell, or, failing that, gnaw through 

 it, and you have a perfect kernel, the liv- 

 ing germ of the second law, from which 

 so much valuable fruit has sprung. 



The simplicity of the proof makes the 

 nut hard cracking for some. He holds 

 that evidently heat is of such a simple, 

 homogeneous nature that all its differential 

 elements must have the same effect, and, 

 further, that all the infinitesimal elements 

 of temperature must have equal effects, 

 which last is analogous to the statement 

 tbft when the camel's back breaks each 



element of weight has the same effect— the 

 first straw being equal with the last in the 

 actual catastrophe. Prom this the division 

 of each element of heat by its absolute 

 temperature and the second law follow 

 easily. 



Secondly, the author's claim that Clau- 

 sius's proof is faulty (as I pointed out 

 years ago) is correct. Clausius proves the 

 form of his function on the principle that 

 in a reversible cycle all natural working 

 substances must be equally efficient, and 

 then attempts to define the function ex- 

 actly by discussing the properties of a 

 perfect gas— a theoretical working fiuid 

 which does not exist in nature. The proof, 

 therefore, fails in default of a further in- 

 vestigation showing that the absence of the 

 natural properties which a theoretically 

 perfect gas lacks does not vitiate the result. 



Theory, Construction and Use of a Pres- ' 

 sure-tube Anemometer: A. F. Zahm, 

 Catholic University, Washington, D. C. 

 The present paper describes the design 

 and use of a pressure-tube anemometer 

 whose observed readings conform to those 

 required by theory. The instrument con- 

 sists of a double-pressure nozzle connected 

 with a differential pressure-gauge. One 

 nozzle transmits the direct impact of the 

 air, while a side nozzle gives the static 

 pressure of the current at the same point. 

 Their difference is theoretically propor- 

 tional to the velocity-head, and serves to 

 determine the velocity of the air when its 

 density is known. To prove the agree- 

 ment of the theoretical and actual pres- 

 sures sustained by the nozzles, the follow- 

 ing facts are experimentally established: 

 (1) The pressure on the direct impact 

 nozzle is proportional to the total head ; 

 (2) the pressure on the side nozzle equals 

 the true static pressure of the point; (3) 

 the differential pressure is proportional to 

 the true velocity head, since the velocity 



