Plymouth is much subject to southerly winds, in conse quence of its being exposed in that quarter, but is shel tered on other sides by the surrounding land. The va pours of the Atlantic having an uninterrupted passage over the town, and becoming condensed by the cold and bleak hills of Dartmoor, occasion a considerable precipi tation of moisture. The average quantity of rain for thirteen years amounts to 324 inches ; a quantity much less than is afforded by many other towns in England. Nevertheless. a considerable humidity exists at all times in the air ; and which is the frequent cause of dense mists, and also of considerable depositions of dew. The quan tity of rain which falls at any one time is in general not considerable ; it chiefly descending in gentle showers. For many days the hygrometer exhibits almost absolute humidity, without any fall of rain ; and, at other times, there is scarcely a day without a shower, for some weeks together. According to Captain Rotheram's accurate register, the number of days in which rain fell was, in 1820, one hundred and fifty-two; in 1821, one hun dred and eighty-four ; and in 1822, one hundred and forty one.
The mean temperature, deduced from the average of six years' ohset vations, is 51°.31 of Fahrenheit ; and, cording to Dr. Brewster's formula, given in his paper on the Mean Temperature of toe earth, in the 9th volume of the Transactions of the Royal Society of Edinburgh, it amounts to 51°,99, agreeing within half a degree of that deduced from observation.
The town enjoys on the whole a considerable share of health ; and its mortality has decreased, in common with the whole country. In 1300, the mortality was one in twenty-seven, and in 1810, one in twenty-eight ; but the mean of the last five years only afforded one in forty -five.
The following is an abstract of the population returns for 1821 : There arc several extensive and important improve ments in a rapid state of advancement in the town and neighbourhood. The most extensive of these is a magni ficent rail-road, proceeding from Sutton Pool to Dart moor; a space of from twenty-five to thirty miles. The country through which it passes is, perhaps, one of the most difficult for an undertaking of the kind, in conse quence of the innumerable inequalities of its surface. A ride over it presents some of the most striking and picturesque scenes, and from which the lover of the bold and irregular aspect of nature may draw the most exqui site enjoyment. The object of its formation is to afford a facility of transport for the fine granite with which the Tors of Dartmoor abound, and to convey into the inte rior, manure, coals, &c. for the line of country through
which it passes.
Two suspension bridges arc also in contemplation; one across the estuary of the Plym, to open a new line of communication with the more southern parts of the coun ty; and the other across the Tamar, at Saltash, to afford a readier communication between Cornwall and Devon. The latter will be of magnificent dimensions ; the distance between the points of suspension of the chains exceeding 800 feet.
Front the diversified country and soil around Plymouth, the botanist can enrich his herbarium with species of al most every genus in the British flora. The woods of Manadon, Tamerton, and Warleigh ; the heaths of Buck land, the rocky district of Shaugh, together with the rich vale of Bickleigh, the banks of the Tamar and Plvm, and an extensive range of sca-coast, present full scope for the exertions of the naturalist, and are such as will amply re ward him for his research.
Of phenogamous plants, upwards of one thousand spe cies have been discovered by Mr. Banks of this place, (author of an introduction to the study of English Botany ;) and in whose intended Flora Plumouthiensis it will be seen that the greater part of English Cryptogamia abounds in this neighbourhood.
At this place the account of Plymouth might with pro priety have ended ; but as no account has appeared in the Encyclnredia, of the large and flourishing town of Ply mouth Dock, in which the great naval arsenal is situated, and as it has been usual to include it under the general denomination of Plymouth, it may be proper to furnish a brief description.
Plymouth Dock is situated at a short distance to the west of Plymouth, its mean latitude being 22' 19" north, and mean longitude 4° 9' 58" west. 1 t owes its origin to the advantages possessed by the noble estuary of the Tamar, called llamoaze, for a safe and commodious harbour for ships of the largest class. Its length is four miles, and its depth, at low water, fifteen fathoms, and contains moorings for ninety-two ships of the line. The town rises from the eastern shore of the harbour, by a gentle and uniform ascent, and its higher parts command ing the most varied and extensive prospects. its form is that of an oblong, the longest side of which measures three thousand feet, and the breadth fourteen hundred, and is surrounded by fortifications. A considerable de gree of regularity has been observed in the construction of the houses, and in the formation of the streets; most of which intersect each other at right angles. Their ge neral width is from thirty to fifty feet.