April i8, 1890.] 



SCIENCE. 



251 



three times in a set of cups, and found that the lighter gave 

 more than ten per cent more wind at five miles per hour, while 

 there vpas no difference between the light and heavy cups in 

 higher veinds. 



4. In the more recent trials in England, an anemometer was 

 placed, with its axis horizontal, on the arm of a whirler, and 

 the whirler rotated once and then suddenly stopped: the ane- 

 mometer cups (supposedly from their momentum) continued to 

 revolve. This experiment was certainly most remarkable. It 

 is a little difficult to see what other result was to be expected. 

 If any thing was to be learned, it could only be by stopping 

 the cups at exactly the moment the whirler was stopped. This 

 certainly does not elucidate in any way whatsoever the sup- 

 posed inertia effect in an intermittent wind. 



5. The crucial test in the English trials was made when the 

 whirler was given an intermittent motion or one simulating a 

 natural wind. The anemometer was placed on the end of the 

 arm, and the velocity of the whirler was changed quite 

 rapidly, ranging back and forth between forty and ten miles per 

 hour, — a far greater fluctuation than can occur in the free air. 

 Here, then, above all things else, we ought to get an inertia 

 ■effect; but it was found that there was no difference in the 

 record of the anemometer between the uniform and intermit- 

 tent motion. The evidence seems to be overwhelming that the 

 ■supposed momentum or inertia effect is purely imaginary. 



We cannot sympathize with the feeling aroused in England 

 by these experiments ; namely, that the Eobinson anemometer 

 is untrustworthy. Undoubtedly the Kew instrument, with its 

 12-inch cups and 24-inch arms, is exceedingly clumsy, and 

 should be discarded as soon as possible; but the experiments in 

 this country have shown that with 4-inoh cups and 6.72-inch 

 arms the results are all that could be asked near ten miles per 

 hour, and during about eighty per cent of our winds. It has 

 also been demonstrated that an anemometer can be constructed 

 which will give very good results over a large range of wind 

 ■velocity. It is very certain that the Robinson anemometer is 

 far ahead of any instrument that requires a vane. In the 

 English trials a vane anemometer or air-meter gave much more 



uniform results than any other instrument in the open air, but 

 this was simply because the effect of the natural wind would 

 be almost exactly counterbalanced on opposite sides of the 

 whirl. In portions of the whirl where the wind vpould tend 

 to accelerate the motion, the much more rapid whirler motion 

 would tend to keep the vane normal to the arm ; and, even if 

 the vane had any influence, it would tend to turn the anemom- 

 eter at an angle with the arm in such a way as to make it lose 

 the proper speed which it would have in its normal position. 



It seems probable that the anemometer problem has nearly 

 reached its solution. What are now needed most of all are 

 experiments with an anemometer, as light as practicable, and 

 which will present a slightly greater proportional resistance to 

 the higher winds than to the lighter, and possibly cause fewer 

 whirls around the cups. H. A. Hazen. 



WashiDgton, April 11. 



Supposed Aboriginal Fish- Weirs in Naaman's Creek, near 

 Claymont, Del. 



The copy of my letter published by the Rev. Mr. Peet in Vol. 

 XII. of the American Antiquarian, March, 1890, No. 2, is correct 

 in some respects, and incorrect in others. So far, Mr. Peet has 

 failed to prove that I ever used the word " pile dwellings," or 

 "river-dwellings." My denial is quite as good as his assertion 

 in this respect, until the original letter be produced, and proven 

 to be mine. I have already given a true version of this letter in 

 a former communication to Science, and sufficient reasons for the 

 use of the terms "pile-structures." '• pile-ends " or "log-ends," 

 and ''stations." They are sutBciently clear explanations for any 

 one to understand without danger of an erroneous impression. 

 No repetition of this explanation is therefore necessary. I call 

 Mr. Peet's particular attention to this assertion. 



In the reproduction of my letter, published on p. 118, Ameri- 

 can Antiquarian, March, 1890, I desire to correct the following 

 error: " The numerous suggestions that the pile-structures were 

 fish- weirs is untenable," should read "the numerous suggestions 

 that the pile-structures were fish-weirs is tenable;" and if my 



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