THE MIDDLE AGES AND DURING THE REVIVAL. 61 



also improved hygrometers (for determining the amount of 

 moisture in the air) ; and as a proof that instruments were 

 made on scientific principles, it may be stated that the spirit 

 of wine and the mercury thermometers were made, the first 

 by the Academy del Cimento in 1655, the second by Halley 

 about 1680, on the principle of relative dilatation. 



Nearly every branch had been seated, at the end of the 

 XVIth century and the beginning of the X Vllth, on a scientific 

 basis viz. : 



Astronomy, Hydrostatics, 



Physics, Optics, 



Mechanics, Electricity, 



Hydraulics, Dynamics. 



Furthermore, great strides had been made in other 

 branches, and if the advance in these was less extraordinary, 

 it sufficed nevertheless to place them also on scientific 

 foundations. 



Zoology was advanced by 



1516 1565. Gesner, who continued the work of Aristotle 

 and the Arabs by his countless observations, and published 

 a celebrated work on ANIMALS, in which he described every 

 known animal, its habitat, habits, food, etc. ; he travelled 

 over a large area of Europe to study fresh-water and marine 

 fish, and collect numerous minerals and plants ; founded the 

 earliest ZOOLOGICAL CABINET in Europe. His book on 

 mineralogy describes the forms of crystals of different 

 minerals, besides fossil shells. 



i^iy 64. Belon studied BIRDS AND FISHES, adding 

 much to the stock of previous knowledge. 



Botany was advanced by 



1498 1554. Tragus, Cassalpinus, and Lobel. 



iSiq 1603. Caesalpinus made valuable additions to 

 this branch ; knew some 1,500 species, 700 of which had 

 been collected by himself. He distributed them into sixteen 

 classes according to their seeds ; was the first to point out 

 the reproductive action of stamens. His CLASSIFICATION 

 was the first attempt of the kind in modern Europe. In 

 other fields he discovered the constant form of CRYSTALLI- 

 SATION in metals, and the increase of weight of metals by 



