"If several large troops," says Charles Darwin, "are turned into one field to graze in the morning, the muleteer has only to lead the _madrinas_ a little apart and tinkle their bells, and, although there may be 200 or 300 mules together, each immediately knows its own bell, and separates itself from the rest. The affection of these animals for their madrina saves infinite trouble. It is nearly impossible to lose an old mule, for, if detained several hours by force, she will, by the power of smell, like a dog, track out her companions, or rather the madrina; for, according to the muleteer, she is the chief object of affection. The feeling, however, is not of an individual nature, for I believe I am right in saying that any animal with a bell will serve as a madrina." Of the attachment that a mule will form for a horse, I will cite an instance from my own observation, which struck me at the time as being one of the most remarkable and touching evidences of devotion that I have ever known among the brute creation. On leaving Fort Leavenworth with the army for Utah in 1857, one of the officers rode a small mule, whose kind and gentle disposition soon caused him to become a favorite among the soldiers, and they named him "Billy." As this officer and myself were often thrown together upon the march, the mule, in the course of a few days, evinced a growing attachment for a mare that I rode. The sentiment was not, however, reciprocated on her part, and she intimated as much by the reversed position of her ears, and the free exercise of her feet and teeth whenever Billy came within her reach; but these signal marks of displeasure, instead of discouraging, rather seemed to increase his devotion, and whenever at liberty he invariably sought to get near her, and appeared much distressed when not permitted to follow her. On leaving Camp Scott for New Mexico Billy was among the number of mules selected for the expedition. During the march I was in the habit, when starting out from camp in the morning, of leading off the party, and directing the packmen to hold the mule until I should get so far in advance with the mare that he could not see us; but the moment he was released he would, in spite of all the efforts of the packers, start off at a most furious pace, and never stop or cease braying until he reached the mare's side. We soon found it impossible to keep him with the other mules, and he was finally permitted to have his own way. In the course of time we encountered the deep snows in the Rocky Mountains, where the animals could get no forage, and Billy, in common with the others, at length became so weak and jaded that he was unable any longer to leave his place in the caravan and break a track through the snow around to the front. He made frequent attempts to turn out and force his way ahead, but after numerous unsuccessful efforts he would fall down exhausted, and set up a most mournful braying.