He has been less of a housekeeper than most, has harvested more wind and storm, sun and sky; abroad night and day with his leash of keen scents, bounding any game stirring, and running it down, for certain, to be spread on the dresser of his page, and served as a feast to the sound intelligences, before he has done with it.  We have been accustomed to consider him the salt of things so long that they must lose their savor without his to season them.  And when he goes hence, then Pan is dead, and Nature ailing throughout.

His friend sings him thus, with the advantages of his Walden to show him in Nature:—­

  “It is not far beyond the Village church,
  After we pass the wood that skirts the road,
  A Lake,—­the blue-eyed Walden, that doth smile
  Most tenderly upon its neighbor Pines;
  And they, as if to recompense this love,
  In double beauty spread their branches forth. 
  This Lake has tranquil loveliness and breadth,
  And, of late years, has added to its charms;
  For one attracted to its pleasant edge
  Has built himself a little Hermitage,
  Where with much piety he passes life.

  “More fitting place I cannot fancy now,
  For such a man to let the line run off
  The mortal reel,—­such patience hath the Lake,
  Such gratitude and cheer is in the Pines. 
  But more than either lake or forest’s depths
  This man has in himself:  a tranquil man,
  With sunny sides where well the fruit is ripe,
  Good front and resolute bearing to this life,
  And some serener virtues, which control
  This rich exterior prudence,—­virtues high,
  That in the principles of Things are set,
  Great by their nature, and consigned to him,
  Who, like a faithful Merchant, does account
  To God for what he spends, and in what way. 
  Thrice happy art thou, Walden, in thyself! 
  Such purity is in thy limpid springs,—­
  In those green shores which do reflect in thee,
  And in this man who dwells upon thy edge,
  A holy man within a Hermitage. 
  May all good showers fall gently into thee,
  May thy surrounding forests long be spared,
  And may the Dweller on thy tranquil marge
  There lead a life of deep tranquillity,
  Pure as thy Waters, handsome as thy Shores,
  And with those virtues which are like the Stars!”

METHODS OF STUDY IN NATURAL HISTORY.

VII.

I come now to an obscure part of my subject, very difficult to present in a popular form, and yet so important in the scientific investigations of our day that I cannot omit it entirely.  I allude to what are called by naturalists Collateral Series or Parallel Types.  These are by no means difficult to trace, because they are connected by seeming resemblances, which, though very likely to mislead and perplex the observer, yet naturally suggest the association of such groups.  Let me introduce the subject with the statement of some facts.