The inhabitants of this city [Dublin] were greatly alarmed yesterday evening, between the hours of four and five, by a most violent concussion of the air, which broke several panes of glass, cracked others, and shook houses to the foundation in an unusual manner, accompanied by a very loud explosion. In the country parts adjacent to the city, the fears of the people led them to imagine that there had been a shock of an earthquake — but the cause proves to have been the explosion of two boats, that were coming down the Grand Canal, freighted with gunpowder from Counsellor Caldbeck’s powder-mills at Clondalklin.
Many lives it was reported were lost; but we can assure the public, from the best authority, that no more than two men were killed, and five or six slightly wounded. The loss from the gunpowder is not estimated to be very great.
It is not as yet ascertained through what manner the fire was suffered to communicate to the powder. It was said that it was from one of the hands having dropped some blazing tobacco from a pipe which he was smoking, but for that there appears no foundation.
Dublin Evening Post 24 April 1787
Irish waterways history 
I can only imagine the fun that the modern day natives of Clondalkin would have if barges were carrying gunpowder!
Brian,
More information at this page – https://localstudies.wordpress.com/2013/09/25/the-1787-explosion-at-corkagh-gunpowder-mills/
Carthach
Excellent; thank you. bjg