Google Ngrams and personal research clearly shows that the spelling of saltpetre is the original. The ER spelling is almost unknown before the mid 1800s
The origins of the word are far from clear see… Saltpetre: The Soul of Gunpowder
Google Ngrams and personal research clearly shows that the spelling of saltpetre is the original. The ER spelling is almost unknown before the mid 1800s
The origins of the word are far from clear see… Saltpetre: The Soul of Gunpowder