118 MR BAIKD ON THE SKA- TREE. 



soon after " nimbus " formed, covered tlie wliole sky, and rain began 

 to fall, continuing tlirougliout the forenoon. It cleared up during the 

 afternoon to line weather, which lasted till the 8th. In the evening of 

 the 7th, about ten p. m., a bank of '• cirro-stratus " was observed hang- 

 ing over the eastern horizon, with the same kind of cirri, the "sea- 

 trees " shooting out of its upper edge and pointing towards the south- 

 west. No particular appearances had been observed, as indicating 

 rain during the day, but the moment I observed this arrangement of 

 clouds, as lighted up by the moon, which had just about eighteen 

 hours before completed her full, I prognosticated that we should have 

 rain next day. An hour afterwards I observed that the whole of the 

 bank of "cirro-stratus," with its accompanying "sea-trees," had 

 passed away, and the night looked still and clear. At seven a. m. of 

 the 8th, however, the sky was already covered with a pretty dense 

 stratum of cloud, very much resembling the passing of " cirro-stratus" 

 into nimbus, and soon afterwards rain fell. The rain continued, with 

 short intervals of fair weather, during the whole day and for most of 

 the night ; and for several successive days, we had abundance of the 

 plumose variety of "cirrus" already mentioned, appearing in the 

 intervals of large " cimiuli," and accompanied, as I have also stated 

 above is usually the case, with showery unsettled weather. 



One of the great uses of the " cirrus," according to nephulologists, 

 is the conducting electricity from one portion of the sky to another, 

 and thus keeping vip the electric equilibrium of the atmosphere — a 

 purpose for which it is exceedingly well adapted, by the fine, tapering, 

 needle-like points, in which cirrose clouds are generally seen to ter- 

 minate. The passing a stream of electricity through a portion of 

 water, produces a rise in the temperature of the water, for " in the 

 transmission of the electric force," says Dr Murray,* " the transmitting 

 medium, under a certain degree of electric intensity conveyed through 

 it, sustains elevation of temperature." The clouds being water in the 

 form of vapour, will in all probability sustain an increase of tempera- 

 ture also, when a current of electricity is passing through them, and 

 thus most likely increase the temperature of the surrounding atmos- 

 phere as well. Even when no clouds are visible, there is stiU. a 

 quantity of watery vapour in the sky, which will be heated by the 

 electric stream. The " sea-tree " being a cloud, the greater part of 

 which consists of a body of fine points, will in aU probability be very 

 intensely active in distributing electricity, and will no doubt, during 

 the time it remains visible, have conveyed a large s portion of this 

 mysterious power through the aqueous vapour, in that portion of the 

 heavens where it is situated, and thus not only have increased the 

 temperature of this vapour, but also of the atmospheric air surrounding 

 it. In the description of the " sea-tree " in the former part of this 



* Mun'ay's Chemistry, vol. i. p. 383. 



