And what is stranger still, this same bone-earth bed crops out on the south side of the chalk at Farnham, and stretches along the foot of those downs, right into Kent, making the richest hop lands in England, through Surrey, and away to Tunbridge.

So that it seems as if the bed lay under the chalk everywhere, if once we could get down to it.
But how does it make the hop lands so rich?
Because hops, like tobacco and vines, take more phosphorus out of the soil than any other plants which we grow in England; and it is the washings of this bone-earth bed which make the lower lands in Farnham so unusually rich, that in some of them--the garden, for instance, under the Bishop's castle--have grown hops without resting, I believe, for three hundred years.
But who found out all this about the Coprolites?
Ah--I will tell you; and show you how scientific men, whom ignorant people sometimes laugh at as dreamers, and mere pickers up of useless weeds and old stones, may do real service to their country and their countrymen, as I hope you will some day.
There was a clergyman named Henslow, now with God, honoured by all scientific men, a kind friend and teacher of mine, loved by every little child in his parish.

His calling was botany: but he knew something of geology.

And some of these Coprolites were brought him as curiosities, because they had fossils in them.

But he (so the tale goes) had the wit to see that they were not, like other fossils, carbonate of lime, but phosphate of lime--bone earth.