In the shallow parts of the river, where the current is rapid, and the bottom pebbly, you may sometimes see the curious circular nests of the Lamprey Eel, Petromyzon Americanus, the American Stone-Sucker, as large as a cart-wheel, a foot or two in height, and sometimes rising half a foot above the surface of the water.  They collect these stones, of the size of a hen’s egg, with their mouths, as their name implies, and are said to fashion them into circles with their tails.  They ascend falls by clinging to the stones, which may sometimes be raised, by lifting the fish by the tail.  As they are not seen on their way down the streams, it is thought by fishermen that they never return, but waste away and die, clinging to rocks and stumps of trees for an indefinite period; a tragic feature in the scenery of the river bottoms worthy to be remembered with Shakespeare’s description of the sea-floor.  They are rarely seen in our waters at present, on account of the dams, though they are taken in great quantities at the mouth of the river in Lowell.  Their nests, which are very conspicuous, look more like art than anything in the river.

If we had leisure this afternoon, we might turn our prow up the brooks in quest of the classical trout and the minnows.  Of the last alone, according to M. Agassiz, several of the species found in this town are yet undescribed.  These would, perhaps, complete the list of our finny contemporaries in the Concord waters.

Salmon, Shad, and Alewives were formerly abundant here, and taken in weirs by the Indians, who taught this method to the whites, by whom they were used as food and as manure, until the dam, and afterward the canal at Billerica, and the factories at Lowell, put an end to their migrations hitherward; though it is thought that a few more enterprising shad may still occasionally be seen in this part of the river.  It is said, to account for the destruction of the fishery, that those who at that time represented the interests of the fishermen and the fishes, remembering between what dates they were accustomed to take the grown shad, stipulated, that the dams should be left open for that season only, and the fry, which go down a month later, were consequently stopped and destroyed by myriads.  Others say that the fish-ways were not properly constructed.  Perchance, after a few thousands of years, if the fishes will be patient, and pass their summers elsewhere, meanwhile, nature will have levelled the Billerica dam, and the Lowell factories, and the Grass-ground River run clear again, to be explored by new migratory shoals, even as far as the Hopkinton pond and Westborough swamp.