382 Proceedings of Philosophical Societies. [May, 



first to bright red, and then to yellow : alkalies, and generally 

 speaking all protoxides, turn it violet ; alumine takes it from 

 water. 



These experiments explain many of the processes in the art of 

 dyeing and colour making, and particularly they explain what 

 happens in dyeing scarlet, and in the manufacture of carmine 

 and lake. 



Lake is composed of carminium and alumine : it has the proper 

 colour of carminium ; that is to say, crimson. Carmine itself is 

 a triple compound of an animal matter, carminium, and an acid 

 which enlivens the colour ; the action of muriatic acid in chang- 

 ing the crimson colour of cochineal into a fine scarlet is similar. 



METEOROLOGY. 



The most apparent causes of atmospheric phenomena, such as 

 the density of the air, its moisture, its heat, and its electricity, 

 appear to depend principally upon the action of the sun : never- 

 theless the irregularity of their efiects in our climates are sufficient 

 to show that there exists influences of a different kind, and that 

 they are complicated with causes still unknown : it is this 

 complication which renders meteorology, even at present, the 

 branch of the physical sciences which has made the smallest 

 approach to that degree of certainty which is necessary to its 

 being considered as a real science. 



M. Humboldt remarks, that if any hope exists that the laws of 

 meteorology can ever be discovered, it must be by studying it in 

 those climates where the phenomena are of the most simple and 

 the most regular nature ; and the torrid zone must, on these 

 grounds, attract the principal notice of observers. 



It is only between the tropics that it has been possible to 

 determine the laws which regulate the small hourly variation of 

 the barometer ; it is in the torrid zone that dry and wet seasons, 

 and that the direction of the winds pecuhar to each season, are 

 submitted to invariable laws. 



M. Humboldt has ptiid much attention to the relation between 

 the declination of the sun and the commencement of the rainy 

 season in the north part of the torrid zone. In proportion as the 

 sun approaches the parallel of any place, the northern breezes 

 are changed for calms, or south easterly winds. The transparency 

 of the air is diminished, the unequal refrangibility of its strata 

 causes those stars to twinkle which are 2U° above the horizon. 

 The vapours scon collect in clouds ; positive electricity is no 

 longer constantly to be found in the lower part of the atmosphere, 

 thunder is heard during the day, heavy rain succeeds, the calm 

 of night is only interrupted by gales from the south-east. 



M. Humboldt explains these appearances by the greater or 

 less inequality between this part of the torrid zone and the neigh- 

 bouring part of the temperate zone. When the sun is to the 



