And telling over these old stories reminds me that I have something that may interest architects and perhaps some other persons.  I once ascended the spire of Strasburg Cathedral, which is the highest, I think, in Europe.  It is a shaft of stone filigree-work, frightfully open, so that the guide puts his arms behind you to keep you from falling.  To climb it is a noon-day nightmare, and to think of having climbed it crisps all the fifty-six joints of one’s twenty digits.  While I was on it, “pinnacled dim in the intense inane,” a strong wind was blowing, and I felt sure that the spire was rocking.  It swayed back and forward like a stalk of rye or a cat-o’nine-tails (bulrush) with a bobolink on it.  I mentioned it to the guide, and he said that the spire did really swing back and forward,—­I think he said some feet.

Keep any line of knowledge ten years and some other line will intersect it.  Long afterwards I was hunting out a paper of Dumeril’s in an old journal,—­the “Magazin Encyclopedique” for l’an troisieme, (1795,) when I stumbled upon a brief article on the vibrations of the spire of Strasburg Cathedral.  A man can shake it so that the movement shall be shown in a vessel of water nearly seventy feet below the summit, and higher up the vibration is like that of an earthquake.  I have seen one of those wretched wooden spires with which we very shabbily finish some of our stone churches (thinking that the lidless blue eye of heaven cannot tell the counterfeit we try to pass on it) swinging like a reed, in a wind, but one would hardly think of such a thing’s happening in a stone spire.  Does the Bunker-Hill Monument bend in the blast like a blade of grass?  I suppose.

You see, of course, that I am talking in a cheap way;—­perhaps we will have some philosophy by and by;—­let me work out this thin mechanical vein.—­I have something more to say about trees, I have brought down this slice of hemlock to show you.  Tree blew down in my woods (that were) in 1852.  Twelve feet and a half round, fair girth;—­nine feet, where I got my section, higher up.  This is a wedge, going to the centre, of the general shape of a slice of apple-pie in a large and not opulent family.  Length, about eighteen inches.  I have studied the growth of this tree by its rings, and it is curious.  Three hundred and forty-two rings.  Started, therefore, about 1510.  The thickness of the rings tells the rate at which it grew.  For five or six years the rate was slow,—­then rapid for twenty years.  A little before the year 1550 it began to grow very slowly, and so continued for about seventy years.  In 1620 it took a new start and grew fast until 1714; then for the most part slowly until 1786, when it started again and grew pretty well and uniformly until within the last dozen years, when it seems to have got on sluggishly.