(c) Obfervations on the Temperature of the Sea at Liverpool, by the late MATTHEW DOBSON, M. D. Communicated by Dr. PERCIVAL. The ingenious Count Marfigli in his philofophical Effay towards a hiftory of the fea, from which the Royal Academy of Sciences at Paris have made a number of extracts, obferved, that the heat of the fea at different depths, provided the depths be very confiderable, is nearly equable; that the degree of heat is about temperate, or fifty-one degrees of Fahrenheit's Thermometer; and that the variations which are difcovered towards the furface, are either the effects of climate, or arife from the particular circumftances of expofure on different coafts. It may be of ufe therefore to afcertain the different temperatures of the fea at different feafons, and on different fhores; that phyficians may with certainty direct their patients to fuch places; and at fuch feafons as are beft adapted to their respective conflitutions and complaints. The variations in the temperature of the fea at Liverpool, are confiderably greater than on any other coaft, and arife from very obvious caufes. The fea, before it enters the river Merfey, is diffufed over a wide extent of flats and fand-banks, which are in many parts left dry, during certain times of the tide. The heat heat of the fummer, therefore, and the cold of the winter have a very powerful effect to alter the natural temperature of the fea. To afcertain thefe variations an experiment was made, about the middle of each month, at high water, and during the time of spring tides. The experiment was made with Fahrenheit's Thermometer, and where the river enters the new dry dock. The firft column of the following table contains the temperature of the fea; the fecond the temperature of the open air in the fhade at eight o'clock in the morning of the fame day during the year 1772; and the third column. the temperature of the external air at two in the afternoon. From this table it appears, that the temperature of the fea at Liverpool, varies during the course of the year 32°. viz. from 36 to 68, or from 15 degrees below to 17 degrees above temperate. It appears likewife, that the sea when warmeft is 14 degrees colder than Buxton Bath, and 30 degrees below the heat of the human body. only four degrees The fame latitude During the months of June, July, and Auguft, the fea is nearly of the fame temperature with Matlock Bath, and in the fucceeding months becomes ftill colder, fo at laft to form an extremely cold bath, above the freezing point. in the temperature of the fea will not occur in other coafts, where the shore is cold, the fea deep, and confequently not expofed in fo fhallow a body to the action of the fun and air. * The heat of Buxton Bath is 82°. that of Matlock 68, according to Dr. Percival's experiments. |