118 MR BAIRD ON THE SEA-TREE. 



cleared up during the afternoon to fine weather, which lasted till the 8th. 

 In the evening of the 7th, about ten P..M., a bank of " cirro-stratus" was 

 observed hanging 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 seve- 

 ral successive days, we had abundance of the plumose variety of " cirrus" 

 already mentioned, appearing in the intervals of large " cumuli," and ac- 

 companied, as I have also stated above is usually the case, with showery 

 unsettled weather. 



One of the great uses of the " cirrus," according to riephelologists, is 

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

 thus keeping up 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 terminate. 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 electrical intensity conveyed through it, sustains eleva- 

 tion of temperature." The clouds being water in the form of vapour, 

 will in all probability sustain an increase of temperature also, when a 

 current of electricity is passed through them, and thus most likely in- 

 crease the temperature of the surrounding atmosphere as well. Even 

 when no clouds are visible, there is still 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 all probability be very intensely active in distributing electricity, 

 and will no doubt, during the time it remains visible, have conveyed a 

 large 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 

 ef this paper, I have stated that the arborescent head of the cloud point- 

 ed toward* the quarter from which the wind blew, and from which the 

 rain afterwards came. Now, if the cloud be situated in the northern 



* Murray's Chemistry, vol. i. p. 383. 



