From "Blood & Rage – A Cultural History of Terrorism" by Michael Burleigh:

Nitroglycerine had been invented by Ascanio Sobrero, a Piedmontese chemist, who by mixing glycerine with sulphuric and nitric acids made a yellowish, sweet-smelling liquid with curious properties. A small quantity blew up in his face. Pursuing a different tack, Sobrero tried a trace on a dog, which died in agony, but which was revealed to have hugely distended blood vessels in its heart and brain. British doctors subsequently discovered that nitroglycerine brought relief for the paralysing pain of angina pectoris. In the 1860s the Swedish inventor Alfred Nobel discovered how to stabilise nitroglycerine by absorbing it into a solid, using such things as kieselguhr, sawdust or gelatine, the end product being sticks of dynamite with names like Atlas. Nobel also invented gunpowder-based detonators to trigger the dynamite explosion.

The Fenian terrorist Rossa endeavoured to bask in the remote glow of the Russian nihilist assassins by advertising in his newspaper courses in manufacturing bombs by a Professor Mezzeroff, 'England's invisible enemy'. Mezzeroff was a tall, sharp-faced man with curly hair arranged around his pate and a 'grizzly moustache', Habitual wearing of black clothes and steely spectacles rounded off the sinister effect of a character straight out of Dostoevsky or Conrad. His origins were mysterious, although he had the accents of an Irishman. His father was Russian, but his mother was said to have been a Highlander and he enjoyed US citizenship. Students were encouraged to pay US$30 for a thirty-day course in making dynamite, although Mezzeroff's enthusiasm was greater than his knowledge of chemistry. He claimed that dynamite 'was the best way for oppressed peoples from all countries to get free from tyranny and oppression'. A pound of the stuff contained more force than 'a million speeches'.

Instead of initiating a burning event, with pressures up to 6,000 atmospheres in milliseconds, dynamite causes a shock wave with pressures of up to 275,000 atmospheres. In other words, compared with gunpowder, a dynamite explosion is like the difference between being knocked off a bicycle by a car and being hit by an express train. Moreover, unlike cumbersome barrels of gunpowder, lightweight dynamite could be concealed within small containers or included in brass grenades whose fragments would cause death and injury when thrown. Different detonators became available to bombers, beyond the gunpowder-based fuses that had to be lit. They included systems based on acids burning through wads of paper pushed into holes in a series of pipes; percussive mechanisms involving timers and a revolver; or alarm clock-based 'infernal machines' that ticked away to oblivion. These enabled terrorists to minimise personal risk by practising place and leave, although there was considerable risk to anyone who happened along. A weapon of such lethality would inevitably entail collateral civilian casualties, even when it was used to decapitate a state's leadership or against fixed strategic assets such as arsenals or dockyards. Hence the anticipatory formulation of ethical evasions before the Fenian campaign had even started.

Dynamite terrorism was the tactic of the weak in an otherwise impossible conflict. There were no immutable laws of war because evolving technologies tended to make them redundant. In any case, as Ireland was not a sovereign state, Irishmen were absolved of international inter-state conventions. In obeisance to the spirit of the Victorian era, the ultimate rationalisation was that dynamite was the apogee of scientific warfare. Hence the respect accorded to Mezzeroff, later immortalised as the 'Professor' by Joseph Conrad in The Secret Agent.