Science . our large, long-tailed ichneumonily, and on its oviposition, only comparativelyfew have watched the process long enough toverify its details, and that, in fact, some ofthese details have never been clearly estab-lished though Megarhyssa is common inmany localities. Does not this indicate thatwe have been neglecting the ecological for thesystematic aspect of entomology? Werner MarchandMendham, N. J. A CONDENSATION PUMP Condensation pumps of the following par-ticular type have been used in our work fora number of years and the design seems to pos-sess sufficient advantages over others
Science . our large, long-tailed ichneumonily, and on its oviposition, only comparativelyfew have watched the process long enough toverify its details, and that, in fact, some ofthese details have never been clearly estab-lished though Megarhyssa is common inmany localities. Does not this indicate thatwe have been neglecting the ecological for thesystematic aspect of entomology? Werner MarchandMendham, N. J. A CONDENSATION PUMP Condensation pumps of the following par-ticular type have been used in our work fora number of years and the design seems to pos-sess sufficient advantages over others in bothsimplicity and compactness to merit this note. The method of operation of this pump, inwhich the exhausting process is accomplishedin two stages, will be made clear by referenceto the cut. In the initial or rough stage,A, the mercury vapor is ejected at relatively high pressure from a small nozzle into a longnarrow throat. The nozzle opening is made suf-ficiently small that the pressure of the vapor. Pig. 1 in the boiler, instead of being practicallylimited to 2 or 3 millimeters, as in the case ofthe ordinary vapor pump, may attain a valueof 75 millimeters or more depending upon theheating. The efficacy of this arrangementwas first pointed out by Stimpson.^ The evac- 1 Washington Acad. Sci. J., 7, pp. 477^82, , 1917. December 16, 1921] SCIENCE 609 uation is completed througli the fine stage,B. In this unit a portion of the high-pres-sure vapor from the central tube is allowedto expand to a low pressure through one ortwo small openings into the inverted cup, vapor then escapes freely into the largewater jacketed tube and gives the conditionsessential for high-speed exhaustion. Tt has found that the high-pressure stageoperating alone, without assistance from thelow-pressure unit, will produce a high speed of the high-pressure unit by itself,however, is very much less than that of thecombination, which possesses a speed compar-able with that of a si
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