Yorkshireman wrote:
Could an intentionally shaped hole have been a forerunner of shaped charges?
Not realy, apart from insomuch as you are directing a line of fracture.
The shaped charge (Munroe effect) sort of works by focusing the detonation wave upon a particular point. The charge requires a stand off from the "burden" & in solid rock is pretty ineffective, in rather the same way as an adobe charge is - it needs a free face opposite the charge in order to work. Also you need an explosive with a high VOD and density (ie high brissance)- blasting gelatine having the lowest brissance (that I know of) that reliablely is used in such a way. Black powder certainly would not normaly suit the bill.