VOYAGE TO ALGERIA. 163 



We turned to the left, so as to cut across her bows. 

 Five minutes' pull would have brought us up to her. 

 The officer waved his cap and I my hat. ' If they could 

 only see us, they might back to us in a moment.' But 

 they did not see us, or if they did, they paid us no at- 

 tention. I returned to the ' Urgent,' discomfited, but 

 grateful to the fine fellows who had wrought so hard to 

 carry out my wishes. 



Glad of the quiet, in the sober afternoon I took a 

 walk towards Europa Point. The sky darkened and 

 heavy squalls passed at intervals. Private theatricals 

 were at the Convent, and the kind and courteous Go- 

 vernor had sent cards to the eclipse party. I failed in 

 my duty in not going. St. Michael's Cave is said to rival, 

 if it does not outrival, the Mammoth Cave of Kentucky. 

 On the 28th Mr. Crookes, Mr. Carpenter, and myself, 

 guided by a military policeman who understood his work, 

 explored the cavern. The mouth is about 1,100 feet 

 above the sea. We zigzagged up to it, and first were 

 led into an aperture in the rock, at some height above 

 the true entrance of the cave. In this upper cavern 

 we saw some tall and beautiful stalactite pillars. 



The water drips from the roof charged with bicar- 

 bonate of lime. Exposed to the air, the carbonic acid 

 partially escapes, and the simple carbonate of lime, 

 which is hardly at all soluble in water, deposits itself as 

 a solid, forming stalactites and stalagmites. Even the 

 exposure of chalk or limestone water to the open air 

 partially softens it. A specimen of the Redbourne 

 water exposed by Professors Graham, Miller, and Hof- 

 mann, in a shallow basin, fell from eighteen degrees to 

 nine degrees of hardness. The softening process of Clark 

 is virtually a hastening of the natural process. Here, 

 however, instead of being permitted to evaporate, half 

 the carbonic acid is appropriated by lime, the half 



