90 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



third cloud was formed on j^assing from 16.1 to 13.8 inches, 

 the fourth on passing from 13.8 to 10.7 inches, and a fifth on 

 passing from 10.7 to 8.5 inches. These barometric pressures 

 correspond respectively to altitudes above the sea of about 

 8000, 15,000, 19,000, 23,000, and 27,000 feet, and the clouds 

 successively formed were of diminishing grades of delicacy, 

 those formed in the rarest medium being extremely delicate 

 and evanescent. For all further degrees of expansion Meiss- 

 ner was unable to perceive any cloud vesicles, although mi- 

 nute transparent drops were present. These results would be 

 directly applicable to our atmosphere had Meissner been able 

 to reduce the temperature of his receiver to that experienced 

 in the upper regions of the atmosphere. Zeitschrift fur Me- 

 teorologie, January, 1873. 



THE DANGERS OF LIGHTJ^ING. 



In Germany there exist insurance companies providing 

 specially against loss by stroke of lightning, and in the in- 

 terest of these special care has been taken to preserve the 

 statistics of liohtnino* strokes, the resultins: loss, and the eflect 

 of lightning-rods. From a recent report we take the follow- 

 ing statistics: In the thirty-one years from 1841 to 1871, in 

 Saxony, 2239 cases of damage by lightning were recorded, of 

 which 1293, or 58 per cent., were cases of " hot strokes " (1 e., 

 they set fire to the material), and 946, or 42 per cent., were the 

 so-called "cold strokes." The total damage is estimated at 

 15,000,000 thalers. In consequence apparently of the increas- 

 ing number of hard roofs (metallic roofs, slate roofs etc.), the 

 ratio 5f hot to cold strokes has apparently diminished, and 

 for the seven years, for example, from 1864 to 1871, the ratio 

 is 46-|- per cent, of hot strokes to 53^ of cold. Of the strokes 

 falling on dwellings with hard roofs, only 22 per cent, set 

 fire thereto, while of those falling on houses with soft roofs, 

 (wooden roofs, thatched roofs, etc.), 73 per cent, were ignited. 

 The lightning appears, in the instant of striking, to lose re- 

 markably its power of firing the object struck, often leaving 

 a building entirely unhurt when it does not at first meet 

 some combustible substance. The denser the body, and the 

 better it conducts heat, the less is the power of the light- 

 ning to fire it ; and a stroke falling first on such a body never 

 sets fire to any thing that it may afterward encounter in its 



