APPENDIX. 453 



more striking example of the opposition or contrast of the laws of 

 animate and inanimate nature — of the forces of inorganic chemical 

 affinity, and those of the powers of life. Vegetables, in such a 

 temperature, and every where surrounded by food, are produced with 

 a wonderful rapidity ; but the crystallizations are formed with equal 

 quickness, and are no sooner produced than they are destroyed 

 together. Notwithstanding the sulphureous exhalations from the 

 lake, the quantity of vegetable matter generated there, and its heat, 

 make it the resort of an infinite variety of insect tribes ; and even in 

 the coldest days in winter, numbers of flies may be observed on the 

 vegetables surrounding its banks, or on its floating islands. Their 

 larvae may also be seen there, sometimes incrusted and entirely de- 

 stroyed by calcareous matter, as well as the insects themselves ; and 

 various species of shell-fish that are found amongst the vegetables 

 which grow and are destroyed in the travertine on its banks. Snipes, 

 ducks, and other water-birds, often visit these lakes, probably attracted 

 by the temperature and the quantity of food in which they abound ; 

 but these usually confine themselves to the banks, as the carbonic acid 

 disengaged from the surface would be fatal to them, if they ventured 

 to swim upon it when tranquil. In May 18 — , I fixed a stick on a mass 

 of travertine covered by the water, and examined it in the beginning 

 of the April following, for the purpose of determining the nature of 

 the depositions. The water was lower at this time ; yet I had some 

 difficulty, by means of a sharp-pointed hammer, in breaking the mass 

 which adhered to the bottom of the stick ; it was several inches in 

 thickness. The upper part was a mixture of light tufa and leaves of 

 confervas ; below this was a darker and more compact travertine, 

 containing black and decomposed masses of confervas; in the 

 inferior part, the travertine was more solid, and of a grey colour, 

 but with cavities which I have no doubt were produced by the 

 decomposition of vegetable matter. I have passed many hours, I may 

 say days, in studying the phenomena of this wonderful lake ; it has 

 brought trains of thought into my mind connected with the early 

 changes of our globe ; and I have sometimes reasoned from the forms 

 of plants and animals preserved in marble in this thermal source, to 

 the grander depositions in the secondary rocks, where the zoophytes 

 or coral polypes have worked upon a grand scale, and where palms 

 and vegetables, now unknown, are preserved with the remains of 

 crocodiles, turtles, and gigantic extinct saurians, which appear to 

 have belonged to a period when the whole globe possessed a much higher 

 temperature. I have likewise often been led, from the remarkable 

 phenomena surrounding me in that spot, to compare the works of man 



