326 



BCmNGB. 



[Vol. VIII., No. 192 



effect here given is due to the actual formation of a 

 partial vacuum produced by the wind blowing across 

 the trap-door, and not to a fault in the barograph, I 

 ■will accept it. Certainly any such effect as this could 

 have been easily learned long ago by the watching 

 of an ordinary barometer. I have watched the ba- 

 rometer, both mercurial and aneroid, in very high 

 winds, and have never seen any thing at all like this 

 effect. GrAN. 



Oct. 1. 



Constitution of the earth. 



Reading yesterday the address of the president at 

 the British association for the advancement of science 

 at the recent meeting in Birmingham, it seemed to 

 me, that, in discussing the geology of the Atlantic 

 and the constitution of the earth, too much is ordi- 

 narily attributed to original action of sedimentary 

 deposition. 



In the Scientific American of June 19, 1885, is a 

 section of the earth on a scale of five inches to its 

 diameter. Upon this, in a greatly exaggerated verti- 

 cal scale, are figured the heights of mountains and 

 the depths of the ocean. But in a smaller figure the 

 author shows that the thin line used to describe the 

 circumference would, in its thickness alone, include 

 the whole of the departures of the mountain-peaks 

 and deepest seas from the true circle or ellipse which 

 should represent the outline of the globe. If we sup- 

 pose a five-inch globe of terra-cotta (red and well- 

 burned clay) to be dipped for a few moments into a 

 muddy ditch, when it comes out with a film of water 

 adhering to its surface, this thinnest film filled with 

 animalcules, adhering but so quickly evaporating, 

 will, on this scale, represent all the water contained 

 in all the oceans and lakes ; and the small quantity 

 which the slightly porous terra-cotta globe has ab- 

 sorbed will represent a greater quantity of water 

 than all that is contained, or ever has been contained, 

 in the depths and caverns and fissures of the earth 

 itself. 



The microscopic Desmidiaceae, Pleurosigmae, wrig- 

 gling vibriones and bacilli, so well known to modern 

 science, and playing such important parts in life and 

 death of man, will, swimming in the adherent film, 

 be greatly magnified representations of the huge 

 monsters which crawled in the slime of morasses, 

 and swam in the oceans of primeval chaos, when the 

 earth first took form, and ceased to be void. The 

 almost infinitesimal film of water will represent all 

 the water that ever constituted a part of this world 

 in which we live : for science tells us that no violence 

 has ever been able to project a stone beyond the 

 sphere of the earth's attraction, and that no vapor of 

 water, no gas, can float in the thin ether which sur- 

 rounds or penetrates our fifty miles of atmospheric 

 depth. What part, then, in the constitution and for- 

 mation and changes of the matter forming the depths 

 of the earth can this very small proportion of water's 

 sedimentary deposits play in the general construction 

 of the globe ? To us infinitesimal bodies, the sur- 

 rounding rocks are immense. Seen from the planet 

 Mars in connection with the whole mass of the earth 

 what are they ? A skin, an envelope, thinner than 

 the model's adhering watery film. Certainly we are 

 more directly interested in the superficial strata 

 which we can see and feel than in the deep masses 

 of which we can learn so little that we speculate as 

 to whether they are solid or fluid without reaching 

 certainty. But the depths in the general plan and 



constitution of matter far outweigh the surface for- 

 mations. And fire (for they are certainly hot) has 

 had much more to do in moulding the earth than 

 water and its sediments. M. C. Meigs. 



Washington, D.C., Sept. 25. 



The excessive voracity of the female Mantis. 



A few days since, I brought a male of Mantis Carolina 

 to a friend who had been keeping a solitary female as 

 a pet. Placing them in the same jar, the male, in 

 alarm, endeavored to escape. In a few minutes the 

 female succeeded in grasping him. She first bit off 

 his left front tarsus, and consumed the tibia and 

 femur. Next she gnawed out his left eye. At this 

 the male seemed to realize his proximity to one of 

 the opposite sex, and began to make vain endeavors 

 to mate. The female next ate up his right front leg, 

 and then entirely decapitated him, devouring his 

 head and gnawing into his thorax. Not until she had 

 eaten all ©f his thorax except about three millimetres, 

 did she stop to rest. All this while the male had con- 

 tinued his vain attempts to obtain entrance at the 

 valvules, and he now succeeded, as she voluntarily 

 spread the parts open, and union took place. She 

 remained quiet for four hours, and the remnant of 

 the male gave occasional signs of life by a movement 

 of one of his remaining tarsi for three hours. The 

 next morning she had entirely rid herself of her 

 spouse, and nothing but his wings remained. 



The female was apparently full-fed when the male 

 was placed with her, and had always been plenti- 

 fully supplied with food. 



The extraordinary vitality of the species which per- 

 mits a fragment of the male to perform the act of 

 impregnation is necessary on account of the rapacity 

 of the female, and it seems to be only by accident 

 that a male ever escapes alive from the embraces of 

 his partner. 



Westwood quotes from the Journal de physique, 

 1784, an instance in which the female of the European 

 species — Mantis religiosa — decapitated the male 

 before mating ; but I know of no record of a similar 

 occurrence with M. Carolina, nor of the further muti- 

 lation described above. 



Riley, in his ' First monthly report,' p. 151, says, 

 " The female being the strongest and most voracious, 

 the male, in making his advances, has to risk his life 

 many times, and only succeeds in grasping her by 

 slyly and suddenly surprising her ; and even then he 

 frequently gets remorselessly devoured." 



In Packard's ' Guide,' p. 575, we find, " Professor 

 Sanborn Tenney tells me he has observed the female 

 after sexual union devour the male." 



L. O. HOWABD. 

 Washington, D.C., Sept. 27. 



A mummified frog. 



My letter which appeared in your issue of Sept. 24, 

 describing the specimen of a mummified Hyla, con- 

 tained an error, which I here wish to correct. The 

 frog was taken from the McLean county coal-shaft of = 

 Illinois, and not of Pennsylvania, as stated, and the , 

 newspaper account was published in Burlington, 111. 

 There is, however, a McLean county in Pennsylvania, 

 and it was through this fact that the slip in question [ 

 occurred. R. W. Shufeldt. 



Fort Wingate, N. Max., Sept. 29. 



