6 9 6 



THE POPULAR SCIENCE MONTHLY. 



CORRESPONDENCE. 



AERIAL NAVIGATION. 



Messrs. Editors : 



SIR : The writer of the paper in the July 

 Monthly on aerial navigation is certainly 

 mild in nis predictions of success, and still 

 he is much too sanguine, as it seems to me. 

 Besides the employment of a new motor, the 

 recent French experiments have accom- 

 plished nothing not done before. If any- 

 thing, they have emphasized the difficulties 

 long recognized by aeronauts, without be- 

 stowing an iota of anything valuable toward 

 their solution. 



An enormous gas-bag is employed to en- 

 counter atmospheric resistance, and then to 

 overcome that resistance a motive power is 

 employed. It is the old way. One would 

 think that effort would stop in this direction. 

 It seems to be an infatuation similar to the 

 " perpetual-motion " craze, just as persistent 

 and just as hopeless. 



As long as atmospheric resistance on 

 any sort of a gas-bag is so much greater 

 than the power developed by any known 

 motor it is capable of carrying, the task of 

 making a practical air-traveling machine is 

 an impossible one. 



It is the humming-bird process, and 

 seems unfitted to man's use. Why not try 

 the albatross or condor method, where grav- 

 ity is the motive power, all active mechan- 

 ism being dispensed with, and shape and 

 position brought into prominence as the 

 factors of success ? Respectfully, 



I. Lancaster. 



335 WABASn A VENUE, ) 



Chicago, June 29, 1885. j 



HOW THE LOCUST LAYS ITS EGGS. 



Messrs. Editors : 



Dear Sir : During the appearance of 

 the so-called seventeen-year " locust " (Ci- 

 cada septendceim) at this place in 1868, the 

 commonly accepted account of the manner 



in which the female deposited her eggs in 

 the twigs of trees included the statement that 

 a transverse incision was made by the insect 

 below the place where the eggs were depos- 

 ited, causing the twig to break off and hang 

 by the bark only. This was supposed to 

 serve an important purpose in the hatching 

 of the eggs, and was regarded as a remark- 

 able exhibition of instinct on the part of 

 the insect. The fact that the whole woods 

 became brown with dead twigs seemed to 

 give color to the statement. But, having 

 carefully observed the process during the 

 present appearance, it is very clear that the 

 breaking is accidental, and disastrous to the 

 eggs, rather than premeditated and benefi- 

 cial. No incision is made, other than those 

 in which the eggs are placed. Only a small 

 part of the twigs break, and they without 

 any regularity as to the place of fracture. 



Another erroneous statement, which is 

 frequently made, is that the eggs are laid 

 in parallel furrows. The incisions in the 

 wood are V-shaped, starting from a single 

 small hole through the bark at the angle of 

 the V. The furrows are sunk deeply into 

 the hardest part of the wood, the eggs 

 placed in the bottom, and left thickly cov- 

 ered with the hair-like fibers of the wood 

 displaced in making the trench, and left 

 attached at one end. The form of the in- 

 cision seems to be due to the necessity of 

 placing the eggs in solid wood, avoiding the 

 pith. In a number of instances where the 

 incision had accidentally penetrated the 

 pith, the furrow was left incomplete, and no 

 eggs were deposited. 



As may be supposed, ovipositing is at- 

 tended with great labor on the part of the 

 female. Each thrust of the ovipositor re- 

 quires a severe and prolonged struggle ; each 

 furrow, judging by the number of displaced 

 fibers, must require from twenty-five to 

 forty thrusts ; and each female makes many 

 separate furrows. Charles B. Palmer. 

 Yellow Spkings, Ohio, July 7, 1885. 



EDITOR'S TABLE. 



SCIENCE VERSUS IMMORALITY. 



SELDOM has the moral sentiment of 

 the civilized world received so se- 

 vere a shock as it has done in connection 

 with the revelations which a prominent 

 London newspaper has made, within the 

 last couple of months, of the gross and 



inhuman vices practiced in the metropo- 

 lis of the British Empire. One of the 

 worst features in the case is the fact 

 that the enormities referred to have 

 been committed, not by the " dregs of 

 the population," as that expression is 

 commonly understood, but by men of 



