TEA VERTINE. 299 



celebrated cascade of the Anio at Tivoli forms calcareous 

 stalactites, and all the country round has rivulets, caverns, 

 and deposits, where this formation may be seen in progress 

 or completed. 



It varies considerably in structure, some specimens are 

 compact and smooth, others have the appearance of a pet- 

 rified moss, and great varieties may be found among the 

 materials of a single building. It is, however, usually rough 

 and more or less spongy-looking, as above stated, but this 

 structure does not seem to affect its stability, at least, not 

 in the climate of Italy. Whether it would stand long frosts 

 is an open question. The night frosts at and about Home 

 are rather severe, but usually followed by a warm sunny 

 day; thus there is no great penetration of ice. 



Every specimen I have examined shows a remarkable 

 compactness of molecular structure in spite of visible poro- 

 sity. All give out a clear metallic ring when struck, and 

 the intimate surface, if I may so describe the surface of the 

 warm-like structure it sometimes displays, is always clear 

 and smooth as though varnished. To this I attribute its 

 durability. Lest'the above description should appear self- 

 contradictory, I will explain a little further. If melted 

 glass were run into threads, and those threads while soft 

 were allowed to agglomerate loosely into a convoluted mass, 

 it would, as regarded in mass, have a porous or spongy- 

 looking structure, but nevertheless its molecular structure 

 would be compact and vitreous; there would be mechanical 

 but not molecular, porosity. Travertine is similar. 



Have we any travertine in England? This is a practical 

 question of some importance, and one to which I have no 

 hesitation in replying, Yes. There is plenty formed and 

 forming in the neighborhood of Matlock, but that which I 

 have seen on the face of caverns, etc., is not so compact 

 and metal-like as the Italian. This, however, does not 

 prove the entire absence of the useful travertine. Not hav- 

 ing any commercial interest in the search, I have only 

 looked 'at what has come in my way, but have little doubt 

 that there are other kinds besides those I saw. I have also 

 seen travertine in course of formation in Ireland, where I 

 think there is a fine field for exploration in the mountain 



