In the system of European climates, from Rome to Upsal, between the isothermal lines of 59° and 41°, the warmest month adds from 16°.2 to 18° to the mean temperature of the year. Farther north, and also in eastern Asia, and in America, where the isothermal lines bend towards the equator, the increments are still more considerable.

As two hours of the day indicate the temperature of the whole day, there must also be two days of the year, or two decades, whose mean temperature is equal to that of the whole year. From the mean of ten observations, this temperature of the year is found at Buda in Hungary from the 15th to the 20th of April, and from the 18th to the 23d of October. The ordinates of the other decades may be regarded as functions of the mean ordinates. In considering the temperatures of entire months, we find, that to the isothermal line of 35°.6, the temperature of the month of October coincides (generally within a degree) with that of the year. The following Table proves that it is not the month of April, as Kirwan affirms, (Estimate, &c. p. 166.), that approaches nearest to the annual temperature.

As travellers are seldom able to make observations for giving immediately the temperature of the whole year, it is useful to know the constant ratios which exist in each system of climates, between the vernal and autumnal temperatures, and the annual temperature.

The quantity of heat which any point of the globe receives, is much more equal during a long series of years than we would be led to believe from the testimony of our sensations, and the variable product of our harvests. In a given place, the number of days during which the N.E. or S.W. winds blow, preserve a very constant ratio, because the direction and the force of these winds, which bring warmer or colder air, depend upon general causes, on the declination of the sun,- -on the configuration of the coast, and on the lie of the neighbouring continent. It is less frequently a diminution in the mean temperature, than an extraordinary change in the division of the heat between the different months, which occasions bad harvests. By examining between the parallels of 47° and 49° a series of good meteorological observations, made during ten or twelve years, it appears, that the annual temperatures vary only from 1o.8 to 20.7; those of winter from 3°.6 to 5°.4; those of the months of winter from 9° to 10°.8. At Geneva, the mean temperatures of twenty years were as follows:

If, in our climates, the thermometrical oscillations are a sixth part of the annual temperature, they do not amount to one twenty-fifth part under the tropics. I have computed the thermometrical variations, during eleven years, at Paris, for the whole year, the winter, the summer, the coldest month, the warmest month, and the month which represents most accurately the annual mean temperature; and the following are the results which I obtained:

?

c 2

At Geneva, the mean temperatures of the summers were, from 1803 to 1809,

M. Arago has found, that in the two years 1815 and 1816, the last of which was so destructive to the crops in a great part of France, the difference of the mean annual temperature was only 2o, and that of the summer 3°.2. The summer of 1816 at Paris was 59°.9, 4°.7 below the mean of the former. From 1803 to 1813, the oscillations round the mean did not go beyond -2°.9, and +3o4.

In comparing places which belong to the same system of climates, though more than eighty leagues distant, the variations seem to be very uniform, both in the annual temperature and that of the seasons, although the thermometrical quantities are not the same.

ART. IV.-Account of the Captivity of ALEXANder Scott, among the Wandering Arabs of the Great African Desert, for a period of nearly Six Years. With Geographical Observations on his Routes, and Remarks on the Currents of the Ocean on the North-Western Coast of Africa, by Major RENNELL, F. R. S. &c. &c. &c. *.

[This account was drawn up by my friend Mr William Lawson and myself, from notes of many conversations with Alexander Scott, immediately after his return from Africa. He was repeatedly examined by us, both separately and in conjunction. Whilst we guarded as much as possible against stimulating his invention by the nature of our questions, we enforced the necessity of strictly adhering to matters of fact; and the result of our intercourse with him, is a conviction, that what he relates may be depended on, as far as his opportunities and talent for observation extend. His story, remarkably free from personal adventure, or suspicious affectation of accuracy in dates and distances, appeared to us always consistent. Like other persons who have experienced the horrible tyranny of the inhabitants of the African Desert, Scott at first exhibited a considerable degree of mental apathy. We probably have not exhausted all his stock of information; we conceived that the cause of truth would be best served, by chiefly contenting ourselves with what he spontaneously uttered. This account might have appeared more interesting, had it been drawn up as Scott's Own Narrative; but this would have deceived the public. We have, however, adhered strictly to his meaning; and, as nearly as we could with propriety, to the language of an ill-educated seaman. The MS. was submitted to the late excellent President of the Royal Society of London, and to our illustrious geographer Major RENNELL. The information it contained appeared to them so important, that the latter gentleman has been induced to furnish a Map, and the two very valuable Dissertations annexed to this paper.

LIVERPOOL, 24th Oct. 1820.

THOS. STEWART TRAILL.]

ALEXANDER SCOTT, a native of Liverpool, at the age of six

teen years, sailed as an apprentice in the ship Montezuma, commanded by Captain Knubley, and belonging to Messrs J. T. Koster and Company of that port. The vessel sailed on the

It was the original intention of Dr Traill to publish this Narrative in a separate volume, for the benefit of Scott's friends. Upon submitting it, however, to an eminent publisher, it was deemed too short for a separate work; and I availed myself of the opportunity which this circumstance presented, of acquiring it for this Journal-D, B.