130 Master Minds of Modern Science 



fog was quickly cleared for a distance of sixty feet all 

 around. 



For centuries fog has been one of man's worst enemies, 

 and for many years scientists have discussed ways and 

 means of fighting it. In 1870 Professor Tyndall showed 

 that a dust-free space was formed over a hot body such 

 as a red-hot poker. At first it was thought that the heat 

 simply burned up the dust particles or that the rising 

 currents of air blew them away, but a little later Lord 

 Rayleigh proved that the explanation was not as easy as 

 this. In 1883 Sir Oliver Lodge took up the problem, and 

 with the help of the late Professor Clark he proved that 

 what actually happened was a bombardment of the dust 

 particles by molecules, and further experiments proved 

 that this is an electrical action. 



What is a fog? It is caused by particles of dust on 

 which, when the air is still, condense tiny drops of water- 

 vapour. Smoke on one side, mist on the other, and a 

 town fog is a combination of the two. Electrify a cloud 

 and it turns to rain. Sir Oliver Lodge proved similarly 

 that if you electrify a fog the dust or smoke in it is 

 precipitated — it falls to the ground. So came about the 

 interesting experiments which we have described; these 

 prove that if the supply of electric power be sufficient, 

 even the densest fog can be cleared away. 



From his student days Sir Oliver Lodge has taken a 

 keen interest in weather, especially in electrical pheno- 

 mena, and one of his most interesting books, written in 

 1892, deals with protection against lightning. (It is called 

 Lightning Conductors and Lightning Guards, and is pub- 

 lished by Pitman.) 



The lightning conductor was in existence, of course, long 

 before Sir Oliver's time, for the first was erected by 

 Benjamin Franklin on his own house in Philadelphia in 

 the year 1752. Most of us know something about light- 

 ning conductors ; at least we know that they are made of 



