72 Canadian Record of Science. 
and its duration is brief, though the rain-fall may be considerable. 
The accompanying thunder is often terrific, and the lightning vivid 
and destructive. Tall pines are shattered on every hand, and 
cattle are frequently killed; three were killed by one stroke near 
our camp about the middle of August. The showers almost always 
take place in the day-time, and are most common at mid-day and 
in the early afternoon. In fact, it is a common saying in this 
region that it never rains at night. Two partial exceptions to this 
rule occurred during our stay, one in which an unusually severe 
and protracted rain lasted from about 3 o’clock in the afternoon 
until 9 or 10 in the evening; the other, a light shower which 
actually took place in the night. During the latter part of the 
rainy season the showers became less frequent, but extended over 
a larger area and lasted longer. The axis of abundance seems to 
be between San Francisco and Kendrick Peaks, but the greatest 
precipitation occurs on San Francisco Mountain, as would be ex- 
pected from its great altitude. The summit of the mountain is so 
cold that it is occasionally whitened with snow while rain falls at 
its base; and hail-storms are frequent both on the mountain itself 
and throughout the plateau region, many sudden storms taking 
this form. 
Over much of the pine plateau the soil consists of decomposed 
lava, and is so porous that the rain sinks out of sight as it falls, and 
the atmosphere is so dry and evaporation so rapid that a few 
minutes after a shower no traces of it are visible. 
On the arid desert of the Little Colorado rains are infrequent, but 
usually of great violence, producing torrents which cut deep washes 
or ‘“arroyos” in the sun-baked sand and clay. Sometimes cloud- 
bursts deluge large areas, flooding the valleys and destroying mul- 
titudes of the smaller mammals. ‘Three storms of this character 
were witnessed, two of moderate size, the third of great dimen- 
sions, and striking evidences of a fourth were everywhere noticeable 
when we reached the region. This latter almost inundated the town 
of Flagstaff and several other places along the line of the Atlantic 
& Pacific Railway, and left unmistakable evidences of its volume 
and force in various directions, the most impressive, perhaps, being 
the overflow of a crater lake and adjoining craterlet just east of 
Kendrick Peak. The track of the torrent that rushed down the 
sides of this crater, and for a distance through the pine forest 
beyond, suggested a veritable volcanic eruption. 
While following the course of Tenebito Wash across the Painted 
Desert, we saw a heavy rain-storm raging over the high mesas to 
the north and east during the entire afternoon of August 14, though 
not a cloud came between us and the parching sun. Before dark 
a furious wind—the vehicle of a sand-blast—swept down the wash 
between the rows of cliffs which mark its course, abating as night 
came on. About 10 o’clock we were startled by a loud roaring in 
the north, which at first gave the impression that asevere storm was 
advancing upon us, but not a cloud could be seen, and the stars 
shone brightly in every direction. The roaring increased and came 
nearer until it was evident that something was coming down the 
bed of the wash; and in a moment a great wave of thick mud 
rushed past with a tremendous roar, accompanied by a fetid 
stench. ‘The first wave was about 1% metres (5 feet) high, but it soon 
rose to 24 meters (8 feet), where it remained for an hour, and then 
