March 28, 1913] 



SCIENCE 



485 



revolutions per minute, n ^ 5 revolutions per 

 minute (estimated), and r^2/3 ft. (esti- 

 mated). Then if o^l foot, we shall have 

 P = about 150 lbs.; or, if a = 2 ft., P = 75 

 lbs., etc. 



It thus appears that under ordinary condi- 

 tions of flight, the effect of these gyroscopic 

 forces could hardly be serious. 



In conclusion, we note the following simple 

 rule for determining the direction in which 

 the force P will be exerted. (This rule was 

 first published by the writer in the Engineer- 

 ing News for June 21, 1910. See also The 

 Scientific American for November 23, 1912.) 



Imagine the deflecting force (that is, the 

 force which compels the aeroplane to change 

 its direction of flight) to be due to the pres- 

 sure of a flat board against the spinning axle 

 (say in front of the motor), and note the di- 

 rection in which the axle, if rough, would 

 tend to roll along the hoard; this will give the 

 direction in which the (forward) end of the 

 axle will tend to move as the result of gyro- 

 scopic action — that is, the direction in which 

 the force P will act against the (forward) 

 bearing. 



For example, suppose the axle is spinning 

 in the clockwise direction, as seen by an ob- 

 server looking forward, and let the aeroplane 

 make a sharp turn to the left; then the for- 

 ward end of the axle will strive to rise. 

 Similarly, if the aeroplane makes a sharp dive 

 downward, the forward end of the axle will 

 strive to turn to the left. 



Edward V. Huntington 



Harvabd University 



fdr-bearing mammals: an unappreciated 



NATURAL RESOURCE 

 The manor of living nature is so ample, that all 

 may be allowed to sport on it freely; the moat 

 jealous proprietor can not entertain any appre- 

 hension that the game will be exhausted, or even 

 perceptibly thinned. 



In such wise did Dr. Richard Harlam, 

 writing in 1825, comment on the inexhausti- 

 bility of our natural game resources. As late 

 as 1857 the following in substance appears in 

 the report of an Ohio state senate committee: 



The passenger pigeon needs no protection. 

 Wonderfully prolific, having the vast forests of 

 the north as its breeding grounds, traveling hun- 

 dreds of miles in search of food, it is here to-day 

 and elsewhere to-morrow, and no ordinary destruc- 

 tion can lessen its numbers, nor can those killed 

 be missed from the myriads that are yearly pro- 

 duced ! 



The tragic story of the passenger pigeon is 

 familiar to every one. Not so familiar, per- 

 haps, are similar stories which may be told of 

 other species. Fortunately, there is a grow- 

 ing realization that our national resources in 

 wild life are rapidly dwindling, and attention 

 is being directed toward checking the exter- 

 mination. 



This consideration comes not a moment too 

 soon. Unless protective laws are enacted be- 

 fore a species is nearly extinct they can not 

 ordinarily avail much. Nevertheless, vigorous 

 efforts should be made continually not only to 

 conserve species which are still plentiful, but 

 to preserve species which, through our lack of 

 foresight, are on the verge of extinction. 



There is, however, one department of our 

 fauna which, in the opinion of the writer, has 

 hardly received its deserved quota of atten- 

 tion. I refer to the several species of fur- 

 bearing mammals whose pelts have a commer- 

 cial value. The species concerned include the 

 bear, raccoon, skunk, badger, otter, sea otter, 

 mink, marten, fisher, red fox and wolverine. 



It is estimated on fair authority that there 

 are within California alone trappers in the 

 proportion of ten to the county, each of whom 

 makes a possible average of five hundred dol- 

 lars from his annual catch. There are fifty- 

 seven counties, so that five hundred and sev- 

 enty persons with a total income for the fur 

 season of $285,000 a year would on this esti- 

 mate be resident in the state. Two hundred 

 and eighty-five thousand dollars is the interest 

 at four per cent, on $7,125,000. This, or even 

 a quarter of it, would seem to be enough of a 

 commercial asset to be worth at least some 

 legislative consideration. 



On the basis of figures quoted by Ernest 

 Thompson Seton' it appears that an extremely 



'"Life Histories of Northern Animals," 1909. 



