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THE POPULAR SCIENCE MONTHLY 



ing of mathematics and the natural sciences 

 in the grammar-classes be committed to spe- 

 cial professors whenever the funds of the 

 school will permit it and suitable teachers 

 can be obtained ; otherwise, professors of 

 science in the higher classes may perform 

 the duty for an additional compensation ; or, 

 if there is no other way, the ordinary pro- 

 fessor may provisionally give the special in- 

 struction. 



M. Fayc's Theory of the Crnst of the 

 Earth. M. Faye has propounded a new 

 theory of the internal structure of the earth, 

 an important feature of which Is that its 

 solid crust is much thicker under the seas 

 than under the continental masses. The 

 oscillations cf the pendulum and the di- 

 rection of the plumb-line are known to be 

 subject to variations in consequence of the 

 neighborhood of a mountain, or even of a 

 hill, calculations based upon which en- 

 abled Maskelyne to determine the density 

 of the globe. When, however, experiments 

 with the plumb-line and pendulum were 

 applied to table-lands and to the grander 

 mountain-ranges, the deviations correspond- 

 ing to the magnitude of the masses which 

 were expected were not shown. The pen- 

 dulum which is sensitive to the presence of 

 the Great Pyramid of Egypt gives no sign 

 of the neighborhood of the Himalayas. 

 Further than this, a real deficiency of at- 

 traction has been observed upon continents, 

 as if there were a great hollow under them ; 

 and the failure of mountain-masses to de- 

 flect the pendulum has been actually at- 

 tributed to the existence of cavities in them. 

 On the other hand, when the investigation is 

 transferred to the sea, the weight is found 

 to be too great, and is in excess of what is 

 demanded by theory, as evidently it falls 

 short of it on the continents. Hence, if we 

 suppose that there is a lack of matter under 

 the continents, we must also suppose that 

 there is under the seas an accumulation of 

 it above the average for the whole earth. 

 M. Faye suggests, to account for these con- 

 tradictions, that the cooling of the earth is 

 going on faster and has taken place to a 

 greater depth under the oceans than under 

 the continents. The temperature at 12,000 

 feet of depth below the sea is a little higher 

 than the freezing-point ; at the same depth 



under the continental masses it is com- 

 puted to be about 300. The matter is kept 

 at this temperature by the superior strata 

 of earth almost impermeable to heat, and 

 through which the heat that actually escapes 

 is hardly perceptible. The crust of the 

 earth in such a situation can increase in 

 thickness only at the slowest. Under the 

 sea, on the other hand, matter at the same 

 depth is in almost immediate communication 

 with a cold of the freezing-point, and, instead 

 of having some non-conducting strata above 

 it to prevent its escape, the heat is imme- 

 diately absorbed in a cold of polar intensity. 

 A similar difference exists deep in the beds 

 of the submarine rocks, for the water is im- 

 bibed in their pores to a greater depth than 

 in the sub-continental rocks, and the heat is 

 conveyed away from them by the vertical 

 convection of the warmed water rising in 

 them. The more ancient the existing beds 

 of the sea, the greater is the thickness of 

 the crust that supports them as compared 

 with that of the continents. 



Trichinosis on a British School-ship. 



A remarkable outbreak of trichinosis on the 

 British reformatory school-ship Cornwall 

 has recently been brought to the notice of 

 the Government health boards. Up to the 

 23d of September last, the health of the 

 boys had for a long time been good, but, 

 between that day and October 23d, forty- 

 three boys were taken sick, falling ill in 

 batches seven on the 23d, two on the 24th 

 of September, sixteen between the 29th of 

 September and the 1st of October, nine 

 between the 3d and 6th, and the rest at 

 intervals. The outbreak was regarded as 

 one of enteric fever, and the general char- 

 acter and progress of the disease seemed to 

 justify the view. No cause, however, likely 

 to produce such an outbreak could be dis- 

 covered. The hygienic condition of the ship 

 was perfect. The inspector turned his at- 

 tention to the food, and found that none of 

 the officers, who were supplied with distinct 

 food from the boys, were attacked. The 

 boys from a particular mess suffered more 

 than the others, and the tendency of the 

 groups of fresh cases to occur on certain 

 days of the week suggested a connection 

 between the attacks and the salt pork that 

 was served out on Mondays. The body of 



