Notice of the Grotto del Cane. 245 



only at the centre or near it, that a person could stand upright. The 

 floor, and sides to a well-defined horizontal line eight or nine inches 

 above it, appeared moist, and on stepping in, I immediately became 

 sensible of a small degree of warmth up to the same height, although 

 the atmosphere down to the ground was perfectly transparent. The 

 custode first directed me to get on my hands and knees, and to 

 bring my face within the influence of the gas. I took the posture 

 desired, and as I had lowered my head to within a short distance of 

 the ground, and found myself breathing a pure air, was beginning to 

 think the wonders of the grotto far overrated, when I suddenly found 

 myself bolt upright, and on my feet, having been brought there by a 

 sensation as if a thousand needles had been at once thrust into my 

 nostrils. The feeling was like that often experienced after drinking 

 strong soda water, only to an almost overpowering degree. 



The next experiment was a cruel one, but I hope pardonable, in 

 as much as the cruelty was far from being of a wanton kind. The 

 man looked for a dog which he had brought with him, and tied to 

 some bushes near the door, and taking the struggling animal in his 

 arms laid him down in the deepest part of the cave. The dog laid 

 quiet for a moment, and then, with a sudden start, nearly escaped 

 from the custode's hands, but was brought back, and once more held 

 down within the full power of the gas. His struggles were violent, 

 and his eyes, turned upward toward his master, showed a high de- 

 gree of suffering ; but presently, his muscles began to relax, and 

 his struggles ceased, his open and beseeching eye only showing life. 

 His master now took him up, and laid him in the pure air, outside 

 the cave. Here he remained motionless for nearly two minutes, 

 when he was seized with violent spasms, gasped for breath, at length 

 got on his feet, staggered about, and then recovering himself fully, 

 darted away into the bushes. A whistle brought him back, and he 

 came up, wagging his tail, to receive the customary crust of bread. 

 The man now lighted a couple of torches, and placing one in my 

 hand, allowed me to amuse myself with such experiments as are fre- 

 quently practised in our Laboratories with this gas, and others of a 

 similar character. The flame began to separate from the torch as 

 soon as it was lowered to the line noticed above, showing a smooth 

 uniform surface to the gas. When moved along the sill of the door, 

 it burnt with undiminished brightness, except where a small channel 

 was made by an inequality in the wood ; when it sunk into this, the 

 light was immediately extinguished, In the same manner, I could 



Vol. XXIV.— No. 2. 32 



