280 ANNUAL OF SCIENTIFIC DISCOVERY. 



days, for the purpose of continuing observations." In relation to the 

 effect of this vast height upon the constitution, M. Khanikoff observes : 

 "This elevation does not make itself felt except on the organs of 

 respiration which are considerably oppressed by the rarity of the 

 air ; of which the mean pressure on the sea-coast corresponds with a 

 height of mercury in the barometer of 760 millimetres, while on the 

 summit of Ararat it was only 410 millimetres. This causes a certain 

 inconvenience to be felt all over the body, and makes one feel that the 

 circulation of the blood is not carried on as usual. As to the other 

 symptoms indicated by several travellers such as tightness of the 

 skin, loss of blood by the lips, the gums, the ears, and even the eyes, 

 consequent on a nervous excitement resembling delirium, nothing 

 of the kind was experienced by any of us. In fact, the inconveniences 

 of our position, which certainly was not very comfortable, arose not 

 from the height at which we were, but from the cold which prevails 

 at that height to be experienced everywhere around in winter 

 and from the snow on which we lay and in which our little tent was 

 overwhelmed. During the greater part of the time the thermometer 

 was between 9 and 27 Fah., which, with the violent wind that 

 prevails constantly in these regions, forms a temperature not very 

 agreeable." London Athenceum. 



OBSERVATIONS ON THE MAMMOTH CAVE. 



THE May number of Silliman's Journal contains an interesting ac- 

 count of the Mammoth Cave, in a letter addressed to Prof. Guyot by 

 Prof. Benj. Silliman, Jr., who has recently made an exploration of its 

 mysteries ; and also, in connection with Mr. Mantell, made a collection 

 of the animals found there. One atmospheric phenomenon attracted 

 the attention of these gentlemen, and tasked their ingenuity for a sat- 

 isfactory explanation ; viz., the blast of cool air blowing outward from 

 the cave, which renders it nearly impossible to enter with a lighted 

 lamp. If the external air has a temperature of 90 Fahr., the blast 

 amounts to a gale ; but if the air without has a temperature of 59-60, 

 no current is observed, and the flame of a lamp held in a favorable po- 

 sition indicates none. It immediately occurred to me (said Prof. Silli- 

 man) that there must be two currents, one above of warmer air, passing 

 inward, and one below of colder air, passing outward, and the reverse ; 

 but experiment soon satisfied me that this was not the case. Only one 

 current could be discovered, and, on inquiry of our intelligent guide, I 

 found that this phenomenon had attracted his attention, and that he 

 was satisfied, from many observations, that only one current existed, 

 and that this flared out when the external air was above 60, and inward 

 when this was below 60. 



The phenomenon is accounted for by Prof. Silliman as follows : The 

 mouth of the cave is the only communication between the external air 

 and the vast labyrinth of galleries and avenues which stretch away for 

 many miles in the solid limestone. The air in these underground ex- 

 cavations is pure and exhilarating, which may, in part, be accounted 

 for by the nitre beds of incredible extent, as the nitrogen which is 



