which the storm comes, the time of its jiassage across the shi^ 

 and, by subsequent angular observations, determine the length 

 and breadth of the meteor, as measured on the surface of the 

 earth, and also its altitude. The whole disturbance of the at- 

 mosphere, in case of a thunder-storm, is frequently confined to 

 a space of three or four miles in one direction, and from two to 

 three miles in the other. 



The change of the wind should be noted during the approach, 

 passage, and end of the storm, and also the character of the 

 lightning, whether sheet, zig-zag, or ramified, and particularly 

 whether it is in the form of a globe or ball of fire. Note also 

 the character of the thunder, whether loud, faint, a sudden ex- 

 plosion, or a continued reverberation. If the ship should be 

 struck all the particulars of the effects produced should be care- 

 fully described. 



During the passage of the electrical discharge along the mast 

 of a ship the natural electricity of all the other parts of the 

 vessel will be disturbed, and in this way efi'ects maybe produced 

 in the cabin not immediately referable to the primary discharge. 



It is stated that thunder storms are not observed on the ocean 

 beyond a certain latitude, and, also, on land, along the north- 

 western coast of America, there are places where they never, 

 or very rarely, occur. Facts in regard to this point are inter- 

 esting. 



19. In case of the occurrence of a tornado or cyclone, every 

 change in the direction and intensity of the wind should be 

 noted, the barometer and thermometer constantly watched, and 

 their indications given, the aj^pearance of the sky, and particu- 

 larly the motion of tho lower and upper clouds, as compared 

 with the surface wind. If the centre of the storm be passed 

 through, a lull will probably be observed coinciding, perhaps, 

 with the lowest altitude of the barometer, and followed by a 

 change in the direction of the wind. If the vessel be in north 

 latitude, and the storm be that of a true cyclone, the direction 

 of its centre may be determined by facing the wind and extend- 

 ing the arms. The right hand will then extend to the centre of 

 the storm. . 



Copies of the logs of all vessels which are subsequently met 

 with that have encountered the same storm should be collected. 



20. In observing the Aurora, note whether an arch be formed 



