Scientific Intelligence — Arts. 399 



By a careful examination of" the above experiments it will be mani- 

 fest that the distance to which the cold water extends from the coast, 

 depends materially upon the depth of the soundings. It barely 

 reaches 40 miles from the shore, where the sea is more than 300 

 fathoms deep, but spreads over double that distance in the shallower 

 parts. At 45 miles from the land, and at a depth of 120 fathoms, 

 the temperature was found to be 45°, that of the sui'face being 56°, 

 and at 60 miles off the land, at 200 fathoms, it was 43°*5, the sur- 

 face being 61°. 



All these circumstances combine to shew that a northerly current 

 of very limited extent, but of considerable force, exists from the Cape 

 of Good Hope along the western coast of Africa ; which, in general 

 terms, may be represented by a volume of Avater 60 miles wide, and 

 200 fathoms deep, averaging a velocity of about a mile an hour, and 

 of the mean temperature of the ocean, running between the shores 

 of Africa and the waters of the adjacent sea. The cloud of mist 

 which hangs over this stream of cold water, is occasioned, of course, 

 by the condensation of the vapour of the superincumbent atmosphere, 

 whose temperature is generally so many degrees higher than that of 

 the sea. It is sufficiently well defined to afford useful notice to sea- 

 men of their near approach to the land. — Sir James Ross's Voyage 

 to the Southern Seas, vol. i., p. 32. 



AETS. 



1 8. On the Curiosities of Glass Manufacture. By Mr A. Pellatt. 

 — In ancient as in modern glass, sand was the base, and alkali the 

 solvent, and the injury occasioned to the glass by an excess of the 

 latter ingredient was pointed out. That opacity of glass called de- 

 vitrification, was explained as consisting in the formation of a mul- 

 titude of minute crystals, in close contact with each other, on the 

 surface of the glass. The process of annealing was then described ; 

 and it was shewn that a glass-tube forty inches in length contracts, 

 if annealed, a quarter of an inch ; while an unannealed tube of the 

 same length contracts but one-eighth of an inch. The most inte- 

 resting part of Mr Pellatt's discourse referred to the mode of mak- 

 ing Vitro di Trino, and of impressing heraldic devices, &c., on glass. 

 In the case of Vitro di Trino, the gathered glass, after being expand- 

 ed into a bulb or cylinder of the required size, has rods of other glass 

 or enamel attached to it in a vertical position, at equal distances all 

 round, and then, the bottom being held, the top part is more or less 

 turned, so as to give an equally inclined twist to the vessel and the 

 rods. A similar but larger vessel is made ; but which is also turned 

 inside out, and then the former is put into the lathe: and, being ex- 

 panded by blowing, the two come together, and adhere by the rods 

 and their intersections, but inclose small portions of air, which, bein'^ 

 regular in size, form, and disposition, give the character of the glass. 

 When heraldic devices, &c., are to be impressed, a mould of the do- 



