30 GENERAL VIEW AND BASIS OF SCIENTIFIC RESEARCH. 



the phenomena of ancieilt eclipses carry us hack towards 

 periods of immense duration ; those of astronomy and the 

 revelations of the telescope indicate to us unlimited space ; 

 the spectroscope points towards the universal distribution 

 of matter ; the phenomena of nature show no definite 

 limits to the quantity of energy ; and the microscope 

 and the phenomena of physics and chemistry reveal to 

 us an almost infinite degree of minuteness in the constitu- 

 tion of substances, and complexity in the action of their 

 forces. 



The number of species of plants and of insects at pre- 

 sent known has been estimated at 100,000. The stars of 

 the firmament cannot be counted, because they exist in 

 myriads ; 200 millions of meteors are estimated to enter 

 our atmosphere every twelve hours, and Arago calculated 

 that 67 millions of comets frequent the planetary orbits. 

 We know that the multitudes of lifeless substances in 

 nature are actually innumerable ; even the smallest grain 

 of sand appears in the field of a powerful microscope like 

 a mass of rock, and therefore composed of an immense 

 collection of smaller particles. As extensive a world of 

 minute things lies beyond the present reach of the micro- 

 scope as that which that instrument has already revealed 

 to us. Notwithstanding the immense number of facts 

 which differ in kind, the number of those which differ in 

 degree is almost infinitely greater, because they shade off 

 into each other by insensible differences. The number of 

 modifications in the quantitative varieties of substances 

 and forces appears to be limitless; even the number of 

 possible mixtures of liquids, or of metals alone, is almost 

 incalculable. 



Berthelot has calculated the number of combinations 

 which may be made of acids with certain alcohols, and 

 says, ' If you give each compound thus possible a name, 



