Nor was it only vegetable life that prospered.  We had, indeed, few birds, and none that had much of a voice or anything worthy to be called a song.  My morning comrade had a thin chirp, unmusical and monotonous, but friendly and pleasant to hear.  He had but one rival:  a fellow with an ostentatious cry of near an octave descending, not one note of which properly followed another.  This is the only bird I ever knew with a wrong ear; but there was something enthralling about his performance.  You listened and listened, thinking each time he must surely get it right; but no, it was always wrong, and always wrong the same way.  Yet he seemed proud of his song, delivered it with execution and a manner of his own, and was charming to his mate.  A very incorrect, incessant human whistler had thus a chance of knowing how his own music pleased the world.  Two great birds—­eagles, we thought—­dwelt at the top of the canyon, among the crags that were printed on the sky.  Now and again, but very rarely, they wheeled high over our heads in silence, or with a distant, dying scream; and then, with a fresh impulse, winged fleetly forward, dipped over a hilltop, and were gone.  They seemed solemn and ancient things, sailing the blue air:  perhaps co-oeval with the mountain where they haunted, perhaps emigrants from Rome, where the glad legions may have shouted to behold them on the morn of battle.

But if birds were rare, the place abounded with rattlesnakes—­the rattlesnake’s nest, it might have been named.  Wherever we brushed among the bushes, our passage woke their angry buzz.  One dwelt habitually in the wood-pile, and sometimes, when we came for firewood, thrust up his small head between two logs, and hissed at the intrusion.  The rattle has a legendary credit; it is said to be awe-inspiring, and, once heard, to stamp itself for ever in the memory.  But the sound is not at all alarming; the hum of many insects, and the buzz of the wasp convince the ear of danger quite as readily.  As a matter of fact, we lived for weeks in Silverado, coming and going, with rattles sprung on every side, and it never occurred to us to be afraid.  I used to take sun-baths and do calisthenics in a certain pleasant nook among azalea and calcanthus, the rattles whizzing on every side like spinning-wheels, and the combined hiss or buzz rising louder and angrier at any sudden movement; but I was never in the least impressed, nor ever attacked.  It was only towards the end of our stay, that a man down at Calistoga, who was expatiating on the terrifying nature of the sound, gave me at last a very good imitation; and it burst on me at once that we dwelt in the very metropolis of deadly snakes, and that the rattle was simply the commonest noise in Silverado.  Immediately on our return, we attacked the Hansons on the subject.  They had formerly assured us that our canyon was favoured, like Ireland, with an entire immunity from poisonous reptiles; but, with the perfect inconsequence of the natural man, they were no sooner found out than they went off at score in the contrary direction, and we were told that in no part of the world did rattlesnakes attain to such a monstrous bigness as among the warm, flower-dotted rocks of Silverado.  This is a contribution rather to the natural history of the Hansons, than to that of snakes.