72 Slatislics.— ^Effect of Heat upon the Colours oJMetah, 



mixed with small qnartzose stones, and with numerous pieces of 

 silver-coloured mica, a vein of stones so regularly placed, that 

 the inhabitants, who for a long time have noticed the appearance, 

 give it the name of The natural wall ; and some naturalists have 

 even maintained that it was a true wall, which might have been 

 constructed in very remote ages by some people now unknown. 

 The stones have generally four faces, are narrower at one oi their 

 ends, and have a small notch below their top. They are ranged 

 horizontally. The kind of wall which thev form is about eigh- 

 teen inches thick, its height, in the place where it is uncovered, 

 is from six to nine feet ; but upon digging into the ground, it has 

 been followed to twelve and eighteen feet deep, Hnd it is already 

 known to extend three hundred feet, and even more, in length. 

 A kind of argillaceous cement fills the intervals between the 

 stones, and coats them externally ; each of the stones is also co-* 

 vered with a layer of ochreous sandy earth. 



M. de Beauvois has brought some of these stones to France,' 

 and, upon being examined by the mineralogists of the Academy,- 

 tbey appeared to possess the characters of basalts ; but, as there 

 have not as yet been found any traces of basalts or of volcanoes 

 in the United States, and as the place where this wall is found 

 is, generally speaking, of a primitive nature, it is possible that 

 this pretended wall is nothing but a bed of trap ; an amphibolic 

 rock, very similar to certain kinds of basalts. 



STATISTICS. 



The superficies of the territory of the United States from the" 

 Atlantic to the Great Ocean is estimated at 2,257,000 square 

 miles, and the population at eleven millions. The proportion 

 of Whites to Blacks has increased as follows since the year 1/90: 

 in that year there were 27 blacks to 100 whites; in 1800 the 

 proportion was 20 to 100; and in 1810 only 19. The number 

 of emigrants that arrived in the different states in 1794 was about 

 10,000 ; in 1817, 22,240, of whom 1 1977 were British or Irish. 

 From the British possessions in America there arrived the same 

 year 2901 individuals. 



By a late survey, finished 26th Feb. last, the population of 

 Glasgow and its suburbs appeared to be 148,798. 



EFFECT OF HEAT UPON THE COLOURS OF METALS. 



M. Chaudet has published a set of experiments, which may 

 have their utility, to determine the appearances which different 

 pure metals exhibit when kept for some time in a strong heat on 

 the cupel, and how these appearances are modified when these 

 various metals are alloyed together. The following are the prin- 

 cipal facts which he has observed : 



(1.) Pure 



