ME. ABEL’S RESEAECHES ON GUN-COTTON. 
249 
the most severe natural conditions of exposure to heat which would ever be likely to 
occur. 
A statement was furnished to General Sabine, by the late Admiral FitzRoy, of the 
maximum and minimum temperatures recorded monthly in the chronometer room of 
Her Majesty’s Ship ‘Odin’ between September 1861 and September 1863, this vessel 
having been during that period at Japan, in the China Sea, Malacca Strait, Indian 
Ocean, Bengal Bay, North and South Atlantic, &c. The highest temperatures recorded 
were in May 1862 and April 1863 (in the Indian Ocean), being 31° (88° F.) on both 
occasions; the minimum temperature in those months were 29° (84° F.) and 26 0, 8 
(80° F.). Between February 1862 and August 1863 the registered maximum tempe- 
ratures ranged between 25°3 and 31°, and the minimum temperatures between 14° ‘7 
and 29°. Admiral FitzRoy considered that, except at times when men were continuously 
at work in a ship’s magazine, the temperature within the latter would be regulated by 
that of the surrounding water, which, at a few feet below the surface, is never warmer 
than from 26° to 30°. If this is the case, the temperature-records obtained from the 
‘ Odin ’ afford a fair representation of the maximum and minimum temperatures of the 
atmosphere in magazines where gun-cotton might be stored on board ship. Steps have, 
however, been taken to obtain records of the maximum and minimum temperatures 
actually experienced in ships’ magazines. 
At the request of General Sabine, Mr. Pogson, the Astronomer at Madras, took daily 
readings, from May 1 to June 30, 1866, of thermometers placed in boxes, the one 
painted black and the other white, and both exposed to the sun. The complete account 
of the observations made by that gentleman have not yet been received, but, in a letter 
to General Sabine, he states that during the above-named period, which occurred in 
the hottest and driest season ever experienced at Madras, the highest temperature regis- 
tered inside the black box was 51 0, 2 (124 0, 4 F.), that in the white box being 44° 
(111°‘2 F.), whilst the lowest minimum readings recorded were 26 - 8(80°F.) in the black 
box, and 26°T C. (79° F.) in the white box*. The maximum temperature recorded in 
the empty Mack box, exposed to the sun at Madras, was therefore about 5° C. below the 
average temperature to which closely packed gun-cotton, in a condition most favourable 
to change, was exposed for about seven hours daily, during three months (having pre- 
viously been similarly exposed to an atmosphere at 50° for an equal period), before there 
was any indication of development of heat, while gun-cotton prepared according to V on 
Lena’s directions resisted a similar exposure for five months, and ordinary gun-cotton 
containing a small proportion of sodic carbonate furnished no indication of change when 
it had been stored under the same circumstances for seven months. 
General MoRiNf, in some observations upon the recent report of Pelouze and Maury 
on gun-cotton, referred to the existence of instances in which the atmosphere in the 
interior of buildings had been raised to a temperature of 38°, 40°, or 42° (the external 
* The difference between the maximum records in the black and white boxes is reported as ranging between 
3° and 7°. f Comptes Eendus, vol. lix. p. 374. 
