On the Temperalure of the Frith of Forth. 3 



. Comparing the mean monthly temperature of the air, as 

 given in this table, with the temperature of the sea for the 

 months in which it was determined, it appears, as might be 

 expected, that there is in the latter a greater uniformity than 

 is observable in the former. 



The summer of 1842 was one of unusually high tempera- 

 ture, as was also the autumn, followed by a winter of ordinary 

 coldness, with the exception of the month of December ; on 

 which account, perhaps, the sea may have been somewhat 

 warmer this year than usual. And owing to the unusual dry- 

 ness of the whole year, the specific gravity of the sea-water 

 may have been a little higher than ordinary. The influence 

 of rain in lowering the specific gravity is indicated in the re- 

 sults obtained in January, February, March, and April. The 

 very low specific gravity of the water on the 5th of February 

 was probably occasioned by an unusual influx of fresh water 

 into that part of the harbour from which the portion tried was 

 taken, brought down by the river (the Water of Leith) that 

 enters the sea near the port. In confirmation of this, it may 

 be remarked, that, on the 2d of April, after some heavy showers, 

 when water taken up at the pier-head was of the specific gra- 

 vity 1.0248, another portion collected at the Light-house stairs, 

 on the harbour side, was so low as 1.0062, seeming to indicate 

 that the fresh water there might even have been floating on 

 the salt. 



The small range of temperature of the sea and air incum- 

 bent, and the general uniformity of the specific gravity of the 

 sea water, as shewn in the first table, putting aside the ex- 

 ception just referred to, is each well marked and remarkable. 

 The equability of temperature of the air, no doubt, mainly 

 depended on that of the water, and this probably not so 

 much on the depth and extent of the Firth itself, as on the 

 circumstance of the tides to which it is subject, connecting, 

 as it were, this narrow sea with the ocean. 



A Greek of Corfu, Nicander Nucius, who visited Britain in 

 the reign of Charles V., happily describes our island as " laved 

 continuously by the ebb and flow of the ocean." To him, 

 accustomed to his own constant lake-like sea, this perpetual 

 flux and reflux, alternately inundating and leaving dry a great 



