720 SEC. 14. METEOROLOGY. 



given on the left-hand margin, and its average weekly death-rate on the 

 right-hand margin. 



B. shows the gross mortality for each year of the period, each epidemic 

 being marked by a different colour. 



By Arthur Mitchell, M.D., F.K.S.E., Chairman of the Medico-climato- 

 logical Committee. Published in the Society's Journal, vol. iv., p. 340. 



2923. Diagram, showing for London the relation of diarrhoea 

 to temperature. Scottish Meteorological Society. 



A. represents the mean temperature of 1859, having the hottest summer in 

 London from 1845 to 1874 ; of 1860, having the coldest summer during the 

 same period ; and of 1861, having an average summer temperature. 



B. represents the mean weekly death-rate in London from diarrhoea during 

 each of these same years, the colours of the diarrhoea curves corresponding 

 with those of the temperature curve for the same years. The weekly death- 

 rate has been calculated in each case at the annual rate of 1,000 of the 

 population. 



By Arthur Mitchell, M.D., F.R.S.E., Chairman of the Medico-climate^ 

 logical Committee. 



2924. Barometric Gradients. 



Scottish Meteorological Society. 



Model illustrative of the principle of the barometric gradient, which is 

 calculated by dividing the distance between any two barometers by their 

 difference in reading, both being reduced to 32 and sea level (or the same 

 level). Designed by Thomas Stevenson, C.E., Honorary Secretary, and 

 described in the Society's Journal, 1867, when the proposal was first made. 



2925. Drawing of an instrument for ascertaining sea and 

 river temperature by thermometers continuously immersed. 



Scottish Meteorological Society. 



The case containing the instruments.is suspended from the pier, or lightship 

 or in the river, and is drawn up bringing with it some water in the cistern at 

 the bottom, in which the thermometer bulbs are placed. Designed by 

 Thomas Stevenson, C.E., F.R.S.E., Honorary Secretary, and described in 

 the Society's Journal, vol. iv., p. 44. 



2926. Cloud Reflecting Compasses. For ascertaining 



direction of higher currents of air. 



Scottish Meteorological Society. 



When a cloud is to be observed the compass should be turned round till one 

 of the hues on the mirror coincides with a well defined edge of the cloud, and 

 the compass is then made to revolve, gradually keeping the hue constantly on 

 the edge of the cloud. The angle indicated by the magnetic needle being 

 afterwards read off, the direction of the cloud's motion in azimuth is at once 

 ascertained. Designed by Thomas Stevenson, C.E., F.R.S.E., Honorary 

 Secretary, and described in the Edinburgh Philosophical Journal, 1855. 



2926a. Hypsometric Map of the Caucasus, recently 

 published by the Topographical Office at Tiflis. 



The Pulkowa Observatory. 



2926b. Diagrams Illustrative of Underground Tem- 

 perature. G. J. Symons. 



