Via Hacker News and Roger Curry’s blog, a description of Alfred Nobel’s dynamite factory in North Ayrshire. H.J.W. Dam writes in McClure’s Magazine (1897) of the many security precautions taken at “The Great Dynamite Factory at Ardeer.” First, all entrants must be stripped of all metal objects that might cause a spark.

To enter the “Danger Area” you must pass the “searcher.” […] He is a tall, military-looking man in a blue uniform faced with red, and he takes from you all metallic objects — your watch, money, penknife, scarf-pin, match-case, matches, and keys. None of these is allowed to be where nitroglycerin is. […]

At this point, too, you get your first glimpse of the “costumes.” A man in a Tam o’ Shanter cap comes up clothed from head to foot in vivid scarlet. He belongs to a nitroglycerin house. Then comes a man in dark blue — a “runner,” or carrier of explosives. Then comes a man in light blue, who belongs to a smokeless-powder factory. […] The different colors are used so that a superintendent at any distance can always tell if a man is on his own ground and attending to his own work.

[…] As you enter the nitrating house your eye is caught by two lead cylinders, five feet in diameter and six feet deep […] At the farther cylinder sits a man in scarlet watching a thermometer. He neither moves, looks up, nor betrays any sign of your presence. The thermometer which he is watching is five feet in length. Only the top or marked portion extends above the cylinder[.] In the cylinder has been placed about a ton and a half of sulphuric acid mixed with a ton of nitric. Into this mixture are now being sprayed 700 pounds of glycerin […] Great heat is caused by the chemical action, and the absolute necessity is that the heat shall be kept down or it will explode the newly formed nitroglycerin. To this end the cylinder is surrounded by a water-jacket, through which cold water is rushing constantly, and four concentric coils of lead pipe occupy the interior of the cylinder, carrying four steady rushes of cold water.

Another alleged aspect of the system, which McClure’s doesn’t mention but Arms & Explosives (1917) does, was that the thermometer-watcher was permitted to rest only on an unstable one-legged stool:

All the operator has to do is to sit on a one-legged stool and watch a thermometer. Should he fall asleep the construction of the stool ensures an automatic and rude awakening. The stool is known as the Scotch system.

(This strikes me as one of the least clever pieces of the system, honestly.) Anyway, resuming Dam’s account of the cylinder-room:

If the heat, through vagaries in the glycerin, rose above the danger point, the thermometer would instantly reveal this to the man on watch. If the thermometer rose ever so little above twenty-two degrees centigrade, the man would turn on more air and shut off the inflow of glycerin. If it continued to rise slowly and he could not stop it by more air and water, he would give a warning shout, “Stand by,” to a man watching below. If it continued, he would shout, “Let her go,” and the man would open a valve; this would sweep the whole charge down to a “drowning-tank” lower down the hill, which would drown the coming explosion in [an] excess of water. The two men the meanwhile would bolt to a safe position behind banks. If the heat rose rapidly, too rapidly for “drowning,” the man would pull the valve, give a warning shout, and run. So would everybody, you included.

Notice the detailed and multi-layered plan here. The “banks” to which Dam refers are earthwork mounds which surround every building in the factory complex.

At half past six on the morning of the 24th of February, one week after the writer’s visit to [the dynamite “mixing-house”], it was the scene of a very disastrous explosion. Twenty-four hundred pounds of nitroglycerin was collected here, in the tanks and boxes mentioned, and from some cause which may never be known it exploded, killing six people — a chemist, a foreman, and four workmen. A few other employees were slightly hurt by flying débris. […] That over a ton of nitroglycerin can explode in the heart of a factory where 1,300 people are at work, and only the six men, within a few feet of it, lose their lives, shows better than any other evidence the meaning and value of the Ardeer mounds.

Speaking of large explosions, I’ve recently been reading primary accounts of the atomic bombing of Hiroshima.

• “The Atomic Bombings of Hiroshima and Nagasaki,” compiled by the Army Corps of Engineers (1946-06-29).

• “Hiroshima,” by John Hersey, in the New Yorker (1946-08-24).

Hersey’s article, which synthesizes many eyewitness accounts from both Japanese and foreign-born occupants of Hiroshima, contains a quotation from Father John Siemes of Tokyo Catholic University; Siemes’ full account of the Hiroshima bombing (including the bit Hersey quotes) is included as an appendix to the Army report.

One particular note from the Army report:

A reference to the various photographs depicting damage [in Nagasaki] shows that although most of the buildings within the effective limits of the blast were totally destroyed or severely damaged, a large number of chimneys even close to X were left standing, apparently uninjured by the concussion. One explanation is that concrete chimneys are approximately cylindrical in shape and consequently offer much less wind resistance than flat surfaces such as buildings. Another explanation is that since the cities were subject to typhoons the more modern chimneys were probably designed to withstand winds of high velocity. It is also probable that most of the recently constructed chimneys as well as the more modern buildings were constructed to withstand the acceleration of rather severe earthquakes. Since the bombs were exploded high in the air, chimneys relatively close to X were subjected to more of a downward than a lateral pressure, and consequently the overturning moment was much less than might have been anticipated.