Foreign Literature and Science. 375 



tributed, which appear as luminous points of a yellowish 

 color. Externally, these pores are covered with cuticle, and 

 some of the larger ones even with rete mucosum ; internally 

 they are lined with delicate cellular tissue. By inflating 

 the skin Dr. D. ascertained that it was not furnished with 

 spiracula, the existence of which he had been led to suspect 

 by some particular circumstances in the physiology of the 

 animal. — Ann. of Phil. 



1 1 . Opposite effects of a change of density of the air, as 

 affecting the going of a clock. — Davies Gilbert, Esq. M.P. a 

 short time ago published some ingenious investigations on 

 the vibrations of pendulums, and shewed, that on a change 

 of an inch in the height of the barometer, an astronomical 

 clock ought to change its rate, in consequence of the altera- 

 tion in the buoyancy of the air, by two tenths of a second a 

 day. Having applied to Mr. Pond and Dr. Brinkley, to ex- 

 amine this point, he was surprised to find they had discovered 

 no such change. On reconsidering the subject, he finds a 

 cause which before he had supposed too small to have any 

 effect, almost exactly counteracting the effect of the change 

 of buoyancy. This cause is the alteration of the arc, by the 

 altered resistance of the air. He remarks : " It is an ex- 

 tremely curious circumstance, that, without any reference to 

 the attainment of this balance between opposite disturbing 

 causes, our clocks should have been fortuitously made to vi- 

 brate, very nearly in the arc which reduces them to equality." 

 For the mathematical investigations and tables illustrative of 

 this singular coincidence, we must refer to the Quarterly 

 Journal of Science for October. — Dub. Phil. Jour. — Ed. 

 Phil. Jour. 



1 2. Distribution of land and water. — From the unequal 

 distribution of the continents and seas, the southern hemis- 

 phere has long been represented as eminently aquatic ; but 

 the same inequality makes its appearance, when we consider 

 the globe divided, not in the direction of the equator, but in 

 that of the meridians. The great masses of land are col- 

 lected between the meridians of 1 0° to the west, and 1 50° 

 to the east of Paris; while the peculiarly aquatic hemisphere 

 commences to the westward, with the meridian of the coasts 

 of Greenland, and terminates to the east with the meridian 

 of the eastern shores of New Holland and the Kurile Isles, 



