P sold the premises to D, knowing it was to be used for the manufacture of dynamite. Damages to P's property were occasioned by an explosion of nitro-glycerine, in process of manufacture into dynamite, in D's powder factory. D's factory buildings were arranged around the slope of a hill. Nearest to P's property was the nitro-glycerine house; next was the washing-house; next were the mixing-houses; then came the packing-houses, and finally, the two magazines used for storing dynamite. These buildings were situated from fifty to one hundred and fifty feet apart, and a tramway ran in front of them. The explosion occurred during working hours and originated in the nitro-glycerine house. Within a few moments of time, in regular order, the explosion of the other buildings with the two magazines coming last. These explosions caused the destruction of P's factory, residences, and stock on hand. All the damages sustained were directly traceable to the nitro-glycerine explosion. All of d's employees engaged in and about the nitro-glycerine factory at the time of the disaster none were killed. So there was no direct evidence as to what caused the catastrophe. P offered expert testimony to the effect that if the factory was properly conducted, and the employees careful during the process of manufacturing, an explosion would not occur. P got the verdict, and D appealed.