Makch 16, 1883.] 



SCIENCE. 



169 



House-flies in the Philippines. 



I remember, years ago, seeing a dried specimen of 

 the house-fly sent to Boston in a letter as a great 

 rarity there, — tlie only one the sender had seen in 

 a year's residence in Manila. As this is one of the 

 constant accompaniments of man, and a sure sign of 

 his presence or vicinity, I was at a loss to account for 

 its absence. It is not even found in the sugar-yards 

 in any great numbers. I now see why it should be so 

 rare; viz., because it could not of itself pass over the 

 six hundred miles of the windy China sea; and the 

 few which might be transported on vessels, if they 

 got ashore from their distant anchorage, would be 

 prevented from multiplying by their numerous ene- 

 mies, — bats, spiders, birds, lizards, and other reptiles. 

 Some days I would not see one, and rarely more than 

 two, around the table. Were they common, with the 

 other insect-pests, life would be almost unendurable 

 in these islands. S. Knbbland. 



Solar corona. 



Various reasons have been assigned for the very 

 conflicting representations of the corona made by 

 observers who have simultaneously sketched it. It 

 seems to me that the principal cause of the very puz- 

 zling differences observed lies iu the fact that the 

 light of the corona falls so near the limit of visibility 

 at the violet end of the spectrum as to excite the ret- 

 ina in different observers unequally. 



I would have each observer tested for color-blind- 

 ness in the part of the spectrum between G- and H; 

 and no doubt as great differences would be found in 

 the sensitiveness of different eyes near the upper 

 limits of visibility as is known to exist in different 

 ears in perceiving sounds near the upper limit of au- 

 dibility. Only those sketches of the corona could be 

 properly compared with each other which were made 

 by observers to whom the relative intensity of the 

 various parts of the spectrum appeared approximately 

 the same. H. T. Eddy. 



Badly crystallized ■wrought iron. 



An iron contractor told me, the other day, that he 

 was called as an expert iu a case where the wrought- 

 iron strap of the walking-beam of a steamboat broke, 

 and injured some one. The broken strap (about four 

 by eight inches in section, I think) was shown, and 

 the interior found to be very badly crystallized, — the 

 worst case, my friend said, he ever saw. The e.xterior 

 was of fair, ordinary texture. Afterwards, a part of 

 the strap was cut off, sawn lengthwise into bars, and 

 tested for tensile strength. All portions were rather 

 weak, the highest resistance being but 36,000 pounds ; 

 but the inner sections, where the iron was worst 

 crystallized, were the strongest of all. 



Does any one know more about this case or any 

 similar one? T. M. Claek. 



178 Devonshire Street, Boston, March 2. 



WHITNEY'S CLIMATIC CHANGES.^ 

 II. 



In the first part of this article the contents 

 of the vohime were described : the author's 

 principal conchisions will now be discussed. 



THE CAUSE OP THE GLACIAL EPOCH. 



Professor Whitney's fundamental postulate, 

 that the general temperature of the ■ atmos- 



^ Continued from No. 5. 



phere is due to heat from the sun, is beyond 

 conti'oversj'. His hypothesis that the inten- 

 sity of solar radiation is graduall}' lessening, 

 hj reason of the dissipation of solar energ}', 

 and that the paleontologic record in arctic and 

 temperate regions is in close sympathy'' with 

 this lessening, will be admitted by most stu- 

 dents. But when he asserts that the degrada- 

 tion of terrestrial climate has been continuous 

 and uninterrupted, the glacial epoch notwith- 

 standing, assent will not so readily be yielded. 

 The idea that the glacial epoch was charac- 

 terized by exceptional cold is all but univer- 

 sally- entertained, and is so plausible on its face 

 that it can be displaced only by cogent reason- 

 ing. 



He advances two lines of argument, — first, 

 that the phenomena of the glacial epoch were 

 produced entii'ely by local causes, such as the 

 elevation of mountains and the submergence 

 of plains ; second, that thej' belonged in the 

 natural order of things to a warmer stage of 

 the earth's climate, and have disappeared by 

 reason of the secular degradation of climate. 

 These two explanations are not clearly rec- 

 ognized as distinct, bat are appealed to in- 

 discriminately in the course of a somewhat 

 desultor}' discussion ; the one being more com- 

 monh' called upon to account for the appear- 

 ance of glaciers, and the other for their 

 disappearance. If temporary local changes 

 are competent to produce local glaciation, they 

 would seem to be equally competent to ter- 

 minate it ; and a secular cause need not be 

 appealed to. If, on the other hand, the gla- 

 ciation of quaternary time has been actually 

 abated by a secular change of temperature, it 

 would seem logical to refer its inauguration 

 also to a secular change. 



The first line of argument is developed chiefly 

 in a discussion of the distribution of glaciers, 

 modern and ancient, with reference to local 

 conditions. This is full of pi'ofitable sugges- 

 tion ; and it is hard to see how any one who 

 has weighed the considerations therein ad- 

 duced can entertain the hypothesis of a polar 

 ice-cap. It appears beyond question, that 

 the only work accomplished bj' the introduc- 

 tion of any conditions of a general nature 

 favorable to glaciation would be the enlarge- 

 ment of existing glaciers, and the institution 

 of limited ice-sheets in favoi'able localities. 

 This, however, is a question of a priori possi- 

 bilities : it is quite another matter to determine 

 whether local conditions can be made to ac- 

 count for tlie ancient magnitude of glaciers. 

 Whitney tells us that they can ; but the only 

 ancient ice-sheet he seriousl}' undertakes to ex- 



