In August 1860, the following was the Dew-Point registered in the Military Hospital, Sierra Leone: REGISTER OF DEW-POINT IN THE MILITARY HOSPITAL, BATHURST, 1 2 3 4 5 6 7 8 9 1 9 10 11 12 13 13 14 15 16 16 Jan. 70-1 65.43 66.76 68-8 62.96 61 33 59 26 60-96 63-10 58 64.7 66.66 61 63 56.99 58.64 63-77 Feb. 57-856-9 51-3 59.3 61.0 58-2 57-9 580 52.1 53.457 64.2 64.4 64 63.2 65.3 March, 59-260-6 59.9 58.5 56.2 55.9 60-6 58.8 57 57.7 58-262-2 66.5 57.5 55.2 55.7 April, 62-662.9 61.6 61-363-4 637 633 65-3 66.2 68-364-266.1 63.9 58.3 64.5 57.1 May, 59.159 59-3 56.7 61-2 58.6 59.8 56 58.8 58.3 59.5 60.5 61.9 57.8 59.7 61.3 June, 57.4 63.6 61.2 59-264.3 601 60.5 62.1 58.6 61 58 61.4 59.5 59.1 59.4 60.9 MONTHS. Jan. ... 52.8 52.2 50-8 58.83 67.2 67.8 62.1 66.6 66.83 67.93 68-66 69.48 59-66 62.76 63.48 62.8 60.63 68-66 Feb. 62.7 63.3 68.7 62.6 62.9 68.5 63.5 650 63.6 66.7 67.7 67.6 March, 57 56.2 54 7 59.8 58.1 56.2 56.3 53.7 54 53.6 55.5 55-3 April, 53.5 58.4 53.5 62.6 65.2 63.6 64.6 64.2 61.7 65.7 71.3 68.8 63.1 58.2 May, 61.5 60.5 60.8 60.5 58.7 63.1 60.1 61 59.4 62.7 61.1 64.3 61.3 64.5 62.2 June, 59 58.5 59.5 67 71.4 67.5 66.1 74.5 65-7 63.1 641 62.8 61.3 61.7 ... 161 CHAPTER VIII. BAROMETRIC PRESSURE OZONOMETER AMOUNT OF CLOUD— NOTATION OF THE WEATHER. principle of. IN 1646, through the independent researches of Pascal and Barometer, Torricelli, it was ascertained that a column of water 34 feet high, and a column of mercury 30 inches high, each exactly counterpoises a column of air of an equal base, extending from the level of the sea to the summit of the atmosphere; and the next year the former observer discovered that there exists a distinct and constant relation between the rise and fall of the mercury in the Torricelli instrument and the changes in the temperature of the atmosphere, produced by rarefaction or condensation, by elevation or descent, each of which is dependent on the unequal distribution of heat. maximum My observations on the barometric pressure in Western Period of Africa are, unfortunately, very limited, but it appears that the and minimum maximum height of the barometer takes place during the observations. blowing of the harmattan winds, and consequently from December to February; and the minimum during the tornado periods, at the beginning and after the rains. The barometer always falls at the approach of rain or wind, and begins to rise during it. The cold, dry, dense air of the harmattan raises the barometric column, whilst the rarefaction of the air preceding the tornado storm depresses it. The greatest range of the barometer in the Gambia, Senegal, and Casamanza, occurs in the month of January; in Sierra Leone in April or May; on L the Gold Coast of Les September, the least range in It has been ascertained that fit every inch which the merroy in the barometer uses or fls, the boiling point of water s based immibed by 1. thendice, if the barometer rises or fills caetenth of an hà there is an elevatire te depression of the Wing print by M 175 F. Mr Führenbait sock kivune † ds a scan the height of Homer a montains, and the perposed the in rir to find the difference in feet berren the riper pilve subios, pare water should be bridled in an open vessel at both stations, and the Hence of tempests a wild in beds shall be multiplied by 3:57 which will gre a die spruinatin to the bright of the upper abere the love subia. From the conjoined temperarons of the atmosphere at the stations, 64a are to be subtracted, and the reminder she malty led by the inedresanti par of the hight day hol so which it is *headed ss tomamn in the Lference of the རྗེས་གས་ད་ཀྱི་ས་མས་ཀྱི་ ཆེས་ ཡིག ཆོ པད A further correct is necessary As an example, let us imagine water to be at the level of barometer," and uses of. by M. Vidi, a native of France, which is called the "Aneroid "Aneroid Barometer." It "consists of a flat circular metallic box, 4 description inches in diameter, and 1 inch thick." Within is an exhausted copper drum, having a thin corrugated upper plate or head. From the centre of this last an upright metallic shaft springs, “which, as it rises or falls by the varying amount of atmospheric pressure exercised on the drumhead," multiplies, through ingenious and complicated springs and levers attached to its upper end, "the delicate movements thus propagated to it;" these are marked by an index which traverses a graduated dial, corresponding in inches and tenths with the scale of the mercurial barometer. I have given a few observations taken with this instrument in the Military Hospital at Sierra Leone. A column of air, extending from the surface of the sea to the top of the atmosphere, which is equal to about 45 to 50 miles, exercises a pressure upon one inch of surface, of 15 lbs., or more correctly, 14.75 lbs.; and according to Professor Schmid of Jena, the entire weight of the atmosphere on the whole surface of the earth is 612,489,851,187,053 tons. An average-sized man exhibits a surface of 15 square feet, or 2160 square inches, and therefore at the level of the sea sustains a total atmospheric pressure, equal in all directions, of 32,400 lbs., or nearly 141 tons. The barometer presents steady diurnal changes, depending on the amount of aqueous vapours. There are two maxima, viz., one at about 9 A.M., and the other at about 10 P.M.; and two minima, one between 3 and 4 P.M., and the other at about 4 A.M.. For the rules necessary to be observed in the use of the barometer as a weather glass, see the introductory chapter. Western At present all the stations of the British, Dutch, and Ozone in Spanish Governments on the West Coast of Africa are more or Africa. less confined to the sea coast. The French Government has most of its stations on the sea coast, and a few in the interior. These stations are well supplied with ozone from their posi**Anu, without, and poúdns. fluid. |