Report on the mortality of cholera in England, 1848-49.

  • Farr, William, 1807-1883.
Date:
1852
Catalogue details

Licence: Public Domain Mark

Credit: Report on the mortality of cholera in England, 1848-49. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    Plague Years—Diagrams. temperature remained high, then cholera rose much liigher; in September the temperature begins to descend, and the cholera line shoots up its highest points, attaining the greatest elevation when the curve of temperature is descending. The form of the cholera curve for all England is very remarkable: the successive terraces and pinnacles of the Plate resemble sections of the primitive mountain formations, surmounted by spires and aiguilles of granite; or recall the lines of a strange Gothic architeclure. The circular diagrams are of a new form, which may serve very well to illustrate periodic phenomena. From the observations of 79 years (1771-1849), Mr. Glaisher had represented the mean temperature of each day of the year by a curve laid down in the usual way on a straight line; and it appeared natural to join the two ends of the line by substituting the radii of a circle for the ordinates, and the angular divisions of the circle for the abscissas. By this arrangement a diagram of a compact form is obtained. It is a modification of the simple dial arrangement in general use. The circle struck round the radii representing the averages—with the dift'erent colouring of the radii xtending beyond and falling short of the circle—makes the diagram represent the facts in a striking miinner to the eye. The diagrams of Plate IV. are described at the foot of the sheet.* A separate diagram for London is given for each of the 11 years from 1840 to 1850. The last diagram represents the average result of the 10 years 1840-9 ; and a new element in the centre —the average length of the day in each week. The radiating power of the sun depends (i) on the time it is above the horizon, and (2) on its angular elevation. As both these elements attain their maximum in the summer solstice, the greatest heating power of the sun is then exerted, but its efiect on the atmosphere goes on accumulating, and the temperature of the air is highest later in the year. The red crescent representing heat on the diagram is deflected 3 weeks to the right; and the blue crescent representing cold is deflected to the same extent. As the greatest effect on the air appears some weeks after the sun has excited its utmost power, so the diseases which excessive hent favours appear some time after the temperature of the air has been highest. Thus the temperature rises above the average at the 17th week, and falls below the average at the 42nd week ; the mortality from summer diseases rises above the average at the 30tb, and falls below the average at the 40th week. In the years 1844, 1846, 1847, 1848, and 1849, it will be seen that the summer mortality exceeds the average when the temperature is for sometime above 60='; and in every year the mortality exceeds the average when the temperature descends below 40° Fahrenheit. London has two healthy and two unhealthy seasons; the first healthy season extends from the 14th to the 29th week, through April, May, June, and the greater part of July ; the second healtiiy season extends from the 40lh to the 47th week, through Oi-tober and November. The first unhealthy season extends over December, January, and February ; the second over August and September. PLAGUE AND CHOLEEA YEARS. The fifth Plate, in a series of eight circular .diagrams, presents a view of the mortality of London in the seasons and weeks of ordinary and plague years. The first two diagrams deserve particular attention; the radii of the Mjwer circles represent the relative average weekly mortality of the years 1840-9 and 1640-6. How much London in the nineteenth is less fatal to its inhabitants than London in the seventeenth century, is evident from these lines; and the improvement is still more striking, when the mortality of cholera—great as it was—is compared with the mortality of the five plagues in the 73 years, 1593-1665. The years 1640-6 have been selected to represent the ordinary city mortality of the 17th century, because the returns are still extant, and are comparatively free from plague. The second diagram represents the average weekly mortality of these years; and it will be observed that there is a great excess of mortality in August, September, October, and part of November. It was the unhealthy season. April, May, and June j * Tfie (irst ciicular diagrams representing the mortalily and temperatme in London during each week, and the diagrams of the plagnes in London, were constrncled in l-'ebruary 1850. The diagrams showing the daily mortality from cholera in England and in tlie 11 Divisions ivere constructed in September i850< .j