Solid masonry of flinty materials

H. Williamson, « My Pond and some of its Inhabitants », Alden’s Oxford Monthly Illustrated Journal, octobre 1871, p.154.

Not the least amusing inhabitant of my pond is the caddis, when in its larva state. It bis well know to the angler as a useful bait. It lives in a tube composed sometimes of sand, something of fine pebbles or bits of stick, or other vegetable materials ; in fact it sets an example worthy of human imitation by adapting itself quickly to whatever circumstances may surround it. I have found its little habitat of all colours and materials, and it is equally at home in a house constructed of the slender leaves of the delicate Callitriche as of the more solid masonry of flinty materials.