VOL. LVII.] PHILOSOPHICAL TKANSACTIONS. 475 



The severe frost of I73g, of which no account appears in the Phil. Trans., 

 began December 2Q, when Lord Charles Cavendish's thermometer in his room 

 stood at 25"; the next evening 11". From this time his lordship placed his in- 

 strument out of the window, and at some distance from it; when in the evening 

 of December 30, it stood at 17". On the morning of Jan. 5, it stood at 13". 

 On the 8th at 15"; the Qth at 14"; 22d at IQ"; 25th at 17". On February 

 5th at 21". During all this time, the thermometer was seldom above 32", the 

 freezing point. 



Thirteen degrees therefore during this frost was the lowest observation, by 

 Lord Charles Cavendish in Marlborough-street. 



At Plymouth, the depth of rain that fell in 1766, was 35 inches. 



XLff^. Of an Electrometer invented by Mr. Lane. p. 451. 



This portable machine was the contrivance of Mr. Read, mathematical instru- 

 ment-maker at Knightsbridge near London. 



The principle on which this electrometer acts is very simple, being merely 

 this; the coated phial is hereby rendered incapable of accumulating and retaining 

 any more than a certain quantity of the electric fluid, for any intended experi- 

 ment, when a metallic or non-electric communication is maile from a screw to a 

 wire loop of the machine, and that quantity will be proportionate to a certain 

 distance, and consequently the explosion and stroke will be thus regulated. The 

 friction glass is a cylinder turned round its axis in a vertical position. 



XLV. Of the Increase and Mortality of the Inhabitants of the Island of Ma- 

 deira. By Dr. Thomas Heberden, F.R.S. p. 46 1. 



When we consider the number of people in Madeira, and the state of the in- 

 habitants, no place appears more proper for forming an estimate of the increase 

 and mortality of mankind than this island; for the number of persons is upwards 

 of 60,000, all of whom may be supposed to live and die in the same place where 

 they received their existence; the accession of strangers and the egression of the 

 natives being so equally inconsiderable, that if the one does not exactly counter- 

 balance the other, the difl^erence may justly be neglected, as of no consequence 

 in the general calculation. This excited Dr. H.'s curiosity; and he procured a 

 survey from house to house in each of the respective parishes; from which, and 

 the parish registers, he deduced the adjoined account. 



Jn Hypothesis. The number of persons in this island, in the year 1743, was 

 48234 of 7 years old and upwards. Now supposing the minors were in the same 

 proportion then, as in this present year, the total of the inhabitants was 53,057. 

 Therefore, by the rule of anatocism, they have increased at the rate of 1,0082 

 per cent, per annum; and by the same rule they double in 84 years 4 months. 



3p 2 



