We went on with our labours but slowly, as many employments diverted us from the great work.

I had discovered that the crystals of salt in our grotto had a bed of gypsum for their base, from which I hoped to obtain a great advantage.

I was fortunate enough to discover, behind a projecting rock, a natural passage leading to our store-room, strewed with fragments of gypsum.

I took some of it to the kitchen, and by repeated burnings calcined it, and reduced it to a fine white powder, which I put into casks, and carefully preserved for use.

My intention was, to form our partition-walls of square stones, cemented with the gypsum.