EXTRACTS FROM FIELD REPORTS AND ABSTRACTS OF LOGS 



OF THE CARNEGIE. 



Synopses of the cruises of the Carnegie, 1909-1916, will be found on pages 164-176. 

 The abstracts of the logs of the Carnegie, given on pages 330-357, contain more detailed 

 information as to the various passages of the vessel and the conditions encountered on them. 



The extracts from field reports pertaining to special observations regarding occurrence 

 of thunder at sea, and to the circumnavigation trip of the Carnegie in sub-Antarctic regions, 

 will be of interest. 



EXTRACTS FROM FIELD REPORTS. 



W. J. Peters and J. P. Ault: Some Notes on the Occurrence op 

 Thunder at Sea, 1915-1916. 



Baron von Humboldt appears to be responsible for the statement that thunder is never heard 

 on the ocean at any great distance from land, though violent electric-storms are often observed at 

 sea and vessels are frequently struck by lightning. Since this statement has provoked discussion 

 from time to time, the following observations made aboard the Carnegie, under J. P. Ault's command, 

 may be of some interest. In accordance with directions issued to the vessel by the Director of the 

 Department of Terrestrial Magnetism, the observations were made on the way from Dutch Harbor, 

 Alaska, to Port Lyttelton, New Zealand, between August 6 and November 2, 1915. As the special 

 object was to obtain some facts on the sound of thunder at sea, it is not likely that thimder audible 

 at the ship occurred without being noted. 



Lightnmg storms or displays were seen on 22 different occasions and they were accompanied 

 by thunder on only 6 occasions, briefly described as follows: 



1. At 8 p. m., August 20, a low, distinct crash and rumblings were heard 7 seconds after the 

 hghtning flashes seen in the west. The nearest lands were the small but rocky island of Attn, of the 

 Aleutian group, about 240 nautical miles distant in a northeasterly direction, and Kamchatka, about 

 420 miles in a northwesterly direction. 



2. From 11 p. m., September 29, to 2 a. m., September 30, blinding lightning flashes were seen 

 at altitudes of about 30° toward the northeast around to the northwest. Only one thunder peal was 

 heard, which was noted at I'' 30" a. m., September 30. The high islands of the Solomon group were 

 the nearest lands at the time, 600 miles away in a southwesterly direction. A gentle easterly breeze 

 was recorded at the time. 



3. Again, near the same group, rolls of thunder were heard with hghtning flashes in the north- 

 west at altitudes ranging from 0° to 50°, on October 7, from 2 a. m. to 5 a. m. A very hght breeze 

 blew from the south at the time. The islands were 250 miles to the southwest. 



4. On October 8, about 5 a. m., heavy rolls of thunder were again heard, 140 miles east of the 

 Solomon Islands. Lightning flashes were observed toward the east at altitudes varying from 0° to 60°. 



5. A heavy roll was heard on October 10 at 9^ SO" a. m., when no lightning was seen. It was 

 followed 15 minutes later by vivid streaks of lightnmg from north to northwest, accompanied by 

 loud thunderclaps. The lightning streaks were seen at various altitudes from 0° to 80°. The first 

 claps of thunder occurred about 20 seconds after the flashes, and the interval gradually decreased to 

 4.5 seconds, to grow to about 20 seconds again, corresponding to an approach and retiring of the 

 storm. The nearest land was the Solomon group, 50 miles to the west. 



6. Thunder was heard during a squall 450 miles northwest of the high land of South Island, New 

 Zealand, on October 27, 1915, at 8 p. m., the hghtning flashes occurring from 70° altitude to the hori- 

 zon, in the north-northwest. Lightning displays were observ^ed again at 5 places on the way from 

 Port Lyttelton to the Samoan Islands, between May 17 and June 7, 1916. Thunder was heard at 

 3 of these. The notes are briefly summarized as follows: 



a. Sheet-hghtning, accompanied by thunder, was seen, May 28 at 9 and 11 p. m. about 5° 

 above the horizon and from southwest to southeast. Flash-hghtning with thunder occurred over- 

 head the next morning, at 5'' 20". About 2 hours later sheet-lightning was observed in the south- 

 east without, however, hearing thunder. The wind during this time came from northwest-by-north 



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