66 THE MAMMOTH CAVE OF KENTUCKY. 



time to refer to two of them. The '^Cascade Hall/' a large cavern^ 

 upwards of two hundred feet in diameter^, and remarkable for a 

 beautiful cascade, delicious water, which sparkles under the Bengal 

 light, and the " Great Western Ship," a huge mass of rock worn 

 by running water into the shape of the stern of a ship, rudder and 

 all, complete. Leaving Silliman's Avenue we enter another of 

 great beauty, called the ''Valley of Roses," from the exquisite 

 crystals of gypsum and carbonate of lime which adhere to it in 

 rose-Hke clusters. Gypsum includes many forms and varieties, 

 most of which are to be found in this interesting valley. There is 

 the alabaster, which sparkles beautifully in the dim light of the 

 lamp ; and the fibrous gypsum, sometimes known as the satin 

 spar ; but the most brilliant specimens are perhaps the transparent 

 crystals of selenite : they consist of rhomboidal prisms, which 

 cleave easily, exposing most beautifully clear surfaces. 



The varieties of carbonate of lime represented in Silliman's 

 Avenue are not the same as in the stalactites, in which case it is in 

 the form termed '' massive," but in the Valley of Roses it appears 

 crystallized, as calcite or calcareous spar in rhomboidal crystals and 

 hexagonal pyramids, the latter forming a variety known as dog- 

 tooth spar. Some of these were very well defined and of large size. 



In order that crystallization may take place, the water requires to 

 be saturated with the substance to be crystallized. The water in 

 the Valley of Roses must, therefore, have been cut off for long 

 periods of time from any fresh supply ; and, thus, there being no 

 dilution, it would in time become saturated with the limestone of 

 which the surrounding rocks are composed. This limestone 

 would of course be a carbonate ; but the water would contain 

 sulphuric acid which, uniting with the lime, would displace the 

 carbonic acid, and form the sulphate of lime or gypsum : the water 

 becoming saturated with the two compounds, crystallization would 

 take place, hence the crystals. But the most wonderful varieties 

 of lime have yet to come. 



On leaving the Valley of Roses, '* Cleveland Cabinet'' is entered: 

 it is the pride of the guides and the wonder of all who behold it -, 



