Gettysburg: Meteorology of the Battle

Notes by Rev. Dr. Jacobs

The extreme weather during and after the Battle of Gettysburg played a role in the health hardships of those who fought. A math professor at Pennsylvania College, Rev. Dr. Michael Jacobs, recorded his meteorological observations during the battle. They were later published in 1885 in the "Star and Sentinel" by his son.

For the Star and Sentinel.

METEOROLOGY OF THE BATTLE

NOTES BY REV. DR. JACOBS.

MR. EDITOR:

While reading, yesterday, the Comte de Paris' thorough account of the battle of Gettysburg, the reference which he makes to the increased heat on the third day, suggested the examination of my father's meteorological records. The results are such that they seem worthy of preservation, as affording data that should be considered in connection with the ever increasing attention given to the topography and incidents of those days. The entire period of the invasion is remarkable for being one of clouds, and, for that season of the year, of low temperature. From June 15th until July 22nd, 1863, there was not an entirely clear day. On the evening before the entrance into our town of Gen. Gordon's division, viz: June 25th, at 8 p. m., a rain began, which some may remember in connection with the arrival of the advance guard of the 25th Pa. militia, under Lieut. Hinkle, of the college company. This rain continued at intervals until Saturday, June 27th, at 7 a. m., the precipitation being in inches 1, - 280. At all the observations made on Saturday and Sunday, and until the nine o'clock observation of Monday night, the entire sky was covered with clouds. On the day before the battle, both at 7 a. m., and 2 p. m., the obscuration was again complete, with cumulo-stratus clouds moving from S.S.E. At 9 p. m., only four-tenths of the heavens were covered. During these days of sombre suspense, the records of the wind are those of almost an entire calm. The thermometer registers as follows during this period:

	7 A.M.	2 P.M.	9 P.M.
June 25th,	59	51	63
" 26th,	60	63	62
" 27th	61	63	67
" 28th	63	67	68
" 29th	66	72	69
" 30	68	79	71

FIRST DAY.-All through the first day, the entire sky was covered with clouds, viz: cumulo-stratus at 7 a. m. and 2 p. m.; and cirro-stratus at 9 p. m. A very gentle southern breeze, (2 miles per hour). Thermometer:

7 A.M.	2 P.M.	9 P.M.
72	76	74

SECOND DAY.-At 8 a. m., sky still covered, (cumulo-stratus). At 2 p. m., three-tenths are clear. At 9 p. m., there are cirrus clouds; wind as on preceding day. Thermometer:

7 A.M.	2 P.M.	9 P.M.
74	81	76

THIRD DAY.-At 8 a. m., sky again completely covered with cumulo-stratus clouds; at 2 p. m., only four-tenths of the heavens are covered, but with cumulus or the massive thunder-cloud of summer; at 9 p. m., seven-tenths cumulus. Wind S. S. W., very gentle. Thunder storm in neighborhood at 6 p. m. The thunder seemed tame, after the artillery firing of the afternoon. Thermometer:

7 A.M.	2 P.M.	9 P.M.
73	87	76

SATURDAY, THE FOURTH.-Rain in showers at 6 a. m., from 2:15 to 4 p. m., and at 4 a. m. of the 5th, aggregating 1.390. Thermometer:

7 A.M.	2 P.M.	9 P.M.
69	72	70

There were slight showers on the 5th and 7th; and on the 8th, a rain from 3 a. m. to 11:30 a. m., which measured 1.300.The maximum temperature for the month of July 1863, was 87(, at the time of Pickett's charge. Eleven days of the month, the maximum was in the seventies, and on one day (17th) it was but sixty-two.The low temperature was undoubtedly a great blessing to the wounded, as well as to all in both armies, in protecting them, in their forced marches, from dangers as fatal as bullets. The frequent rains cleansed the fields of much that would have caused disease. It is, however, for military men to determine what effect the atmospheric conditions had upon the conflict, and to conjecture what result might have followed had we had that year an average July, not to say one of such extreme heat as that through which we have just passed.

II. E. J.GETTYSBURG, July 30, 1885.

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