"This afternoon at about 5 oclok the great explosion of four powder magazene on the Hill north of the City took place, when forty tons of Blasting, sporting, & giant Powder was burned which shook the whole City to its foundations and done tens of thousands of Dollars of Damage in glass alone. I do not know of one house in the City that Entirely escaped damage. It was a miracle that the four building made of Rock, Cobble, Iron & Concrete was blown high into the air & scattered over the City for a circuit of more than a mile with a population of 20,000, and ownly four persons killed. The whole City shook like an Earthquake. Many escaped narrowly from death. Many women fainted. Nearly all the glass was blown out of the New Tabernacle."
[Wilford Woodruff's Journal: 1833-1898 Typescript, Volumes 1-9, Edited by Scott G. Kenney, Signature Books 1993, http://amzn.to/newmormonstudies]