358 



precise account of such thunder-storms, and of the circumstances in 

 which they appear to originate, should be obtained. 



In recording the phenomena of thunder and lightning it is de- 

 sirable to state the duration of the interval between the flashes of 

 lightning and the thunder which follows. This may be done by means 

 of a seconds-hand watch, by which the time of the apparition of the 

 flash, and of the commencement (and of the conclusion also) of the 

 thunder may be noted. The interval between the flash, and the com- 

 mencement of the thunder, has been known to vary in different cases, 

 from less than a single second to between 40 and 50 seconds, and 

 even on very rare occasions to exceed 50 seconds. The two forms 

 of ordinary lightning, viz. zigzag (or forked) lightning, and sheet 

 lightning, should always be distinguished apart; and particular atten- 

 tion should be given both to the observation and to the record, in the 

 rare cases when zigzag lightning either bifurcates, or returns upwards. 

 A special notice should not fail to be made when thunder and light- 

 ning, or either separately, occur in a perfectly cloudless sky. When 

 globular lightning (balls of fire) are seen, a particular record should 

 be made of all the attendant circumstances. These phenomena are 

 known to be of the nature of lightning, from the injury they have 

 occasioned in ships and buildings that have been struck by them ; 

 but they differ from ordinary lightning not only by their globular 

 shape, but by the length of time they continue visible, and by their 

 slow motion. They are said to occur sometimes without the usual 

 accompaniments of a storm, and even with a perfectly serene sky. 

 Conductors are now so universally employed in ships, that it may 

 seem almost superfluous to remark that, should a ship be struck 

 by lightning, the most circumstantial account will be desirable of 

 the course which the lightning took, and of the injuries it occa- 

 sioned ; or to remind the seaman that it is always prudent, after 

 such an accident has befallen a ship, to distrust her compasses until 

 it has been ascertained { that their direction has not been altered. 

 Accidents occurring on land from lightning will, of course, receive 

 the fullest attention from meteorologists who may be within con- 

 venient distance of the spot. 



Auroras and Falling Stars. 

 Auroras are of such rare occurrence in seas frequented by ships 



