424 Miscellaneous Intelligence. [Sept. 



The researches of Don Fausto del Elhuyar, whose fame is so well esta- 

 blished in the history of science and of the raining art, shew that the mean 

 produce of all the mines of Mexico does not exceed 18 to 25 parts of silver in 

 10.000, which is equal to 3 or 4 ounces per quintal (100 lbs.) The calculations of 

 Senor Garros give less than 2 ounces per quintal for the mean produce of all 

 America. The great vein of Guanajuato, the most valuable in the world, has 

 yielded only an average return of 4 ounces per quintal. The proportion of 7% 

 ounces found in the ore from Villa Clara is therefore remarkable ; but not less 

 so is the great facility with which I obtained the metal, by a first experiment, 

 without any guide to regulate the quantity of salt and the proportion of quick- 

 silver, best suited to form the amalgam, which nevertheless was formed within 

 a few hours after throwing in the mercury. It is also to be observed that no 

 " magistral" (precipitant ?) was employed, which is usually indispensable. 



A subsequent article by the same writer, dated January 1829, states that no 

 other silver mine had been discovered, and that the workiug of that of Don Jose 

 de Escalante had made little progress up to that date. G. 



11. Supposed Change of Climate of the Northern Parts of the Earth. 



Our readers are aware, that the opinion of the northern parts of our earth, 

 having formerly possessed a much warmer climate than at present, has been 

 adopted and supported by many naturalists and geologists. The proof of this 

 fact is supposed to be found in the remains of vegetables and of animals, the 

 inhabitants of warm countries, being now found in the rock formations of colder 

 climates. Dr. Fleming, who was the first to shew the weak points of the much 

 talked of speco-diluvian hypothesis of Dr. Buckland, has now taken up the 

 subject of the remains of animals. His opinion is, that the discovery of the 

 remains of a species in any rock formation is no ground for inferring, that the 

 other species of that genus must have been also inhabitants of the same country. 

 He considers, that unless the same species are found in our rocks, which at present 

 inhabit warm countries, nothing certain can be concluded ; as an instance how 

 much analogy may mislead us in this question, he mentions, the genus Equus, the 

 species of which are sufficiently separated in geographical distribution. In like 

 manner he brings forward the elephant, the remains of which found in Siberia 

 have been pronounced by Cuvier to be very probably those of an animal that 

 inhabited a cold country. Analogy is certainly a powerful instrument in the 

 search after truth, but it is to mistake its nature and use altogether, to 

 apply it to the direct establishment of dogmas. It can only guide our enqui- 

 ries ; at most it may shed a ray of light upon our path, and enable us to distinguish 

 and seize the particular truth we are in search of: but it would be to confound all 

 science, to suppose that every analogy is a truth. Analogy cannot be made the 

 foundation of a fact ; but it may form sufficient grounds for enquiring if that 

 fact be true or otherwise. 



Dr. Fleming's paper is in answer to Mr. Conybeare, and taken with the former 

 on Dr. Buckland's deluge, proves him to be an antagonist every way worthy of 

 attention. Both the papers contain detections and refutations of that loose 

 analogical inference, for reasoning it cannot be called, which is the bane of true 

 science. H. 



12. Limestone Formation. 



Professor Sedgwick, in his communications to the Geological Society, of 1831, has 

 shown, that the mountain limestone of the north of England consists essentially of 



