lens

I could not make it out when first I saw the light flashing upon the lens.” He rose and peeped into the hut.

Then with an expression of interest he laid down his cigarette, and carrying the cane to the window, he looked over it again with a convex lens.

And yet they have missed him up to now!” Holmes had gone to the window and was examining with his lens the blood mark on the sill.

Merryweather perched himself upon a crate, with a very injured expression upon his face, while Holmes fell upon his knees upon the floor and, with the lantern and a magnifying lens, began to examine minutely the cracks between the stones.