Here we see summer cyclones formed under the intense solar radiation that beats down through a nearly diathermanous atmosphere upon the wastes of the Rocky Mountain plateaus; cyclones that, if they form in the northern part of the plateau region, move eastward to our Lakes and thence eastward to the St. Lawrence with scant rainfall; cyclones that, if they have their origin farther south in the region of Colorado, move into the Ohio Valley and thence to New England with considerably more precipitation; and cyclones that, if they have their origin anywhere in our southwest States or Texas, or enter our region of observation from the South Pacific Ocean, can always be expected to cause general rainfall when they reach the Lower Mississippi Valley and later as they pass up through the central portions of the continent. Here also one may view the great winter cyclones that originate in the Pacific between Hawaii and the Aleutian Islands and come under our vision as they successfully surmount the formidable barriers of the Rocky Mountains with but little diminution of energy, sweep across our continent with increasing force and heavy precipitation, and within three days pass beyond our meteorological horizon at the Atlantic seaboard only to be heard from several days later as boreal ravagers of Northern Europe. The great anti-cyclones that constitute the American cold waves drift into our territory from Canadian Northwest provinces, and are studied under rapidly changing conditions during three thousand miles of their course. West Indian hurricanes, at sea level and in humid air, which are the most violent of all storms except the American tornado, intrude themselves into the domain covered by the weather map at Florida or the East Gulf coast and usually pass off to the northeast with high winds skirting our southern coast stations.