Color of the Air and of Deep Waters. 71 



it known. Their account excited public curiosity, and boats of con- 

 venient size were made which now serve to introduce amateurs. Its 

 entrance is triangular, having a base of four feet five inches wide and 

 about the same height. The summit is rounded and having but lit- 

 tle thickness, the entrance is easily effected by stooping, when the 

 traveller finds himself in a spacious grotto, the sides and roof of which 

 are remarkably regular. Its extent from the front to the rear, which 

 is the only landing place, is one hundred and twenty five feet and it 

 measures one hundred and forty five feet in a transverse direction. 

 The depth of water at the entrance is sixty seven feet, in the middle 

 of the grotto sixty two feet and at the landing place fifty eight feet. 

 The rock is limestone of a clear grey fracture, and there are no indi- 

 cations of stratification. 



On entering, every thing appears dark except the water which is 

 luminous and of a splendid blue, contrasting with the general obscu- 

 rity. In advancing from the entrance the ends of the white oars 

 shine in the water with a splendid blue light which disappears as soon 

 as they are raised : this is the most singular phenomenon of the azure 

 grotto, for people are puzzled to conceive why objects are so vividly 

 luminous in the water, and no longer so when above the surface. In 

 dipping the hand or a cloth into the water one would think it a blue 

 dye; the whole immersed part is luminous and colored, while the 

 parts without are dark and uncolored. 



At the bottom of the grotto there is a smalf space on a level with 

 the water, where debarkation is effected, and which is the only spot 

 which leads to any suspicion of the work of human hands in the grot- 

 to. It is a kind of bench in the rock about three feet high, on which 

 several persons may conveniently place themselves and examine at 

 leisure the phenomenon of the azure grotto. The light which comes 

 in at the small opening, produces a train of white light, like the re- 

 flexion of the moon from the water when rising, and which extends 

 half way over the sheet. ' The rest of the surface is blue even to the 

 feet of the observer. This color gradually diminishes to the right 

 where the walls of the grotto are farther from the entrance. The 

 train of white light, illuminates also the vault and exhibits it in its 

 natural color, but when the entrance is closed by a boat or more per- 

 fectly by a dark cloth the vault itself becomes blue, reminding one of 

 the effect of burning spirits of wine in a dark chamber. There is 

 then no light but that which proceeds from the water. The experi- 

 ment of the cloth ought to be made by all who wish to enjoy the spec- 

 tacle in its full beauty. 



