The progress of mechanical invention may be responsible for the depression, but it has provided us with a number of means of making it endurable. Not least among these compensatory blessings are the modern methods of keeping cool.

The newest "cure" for hot weather is the air-cooled building, the increasing prevalence of which bids fair to do much more than promote human comfort. It may conceivably produce far-reaching economic and social effects through removing the obstacles imposed by heat upon human undertakings, in the tropics and elsewhere.

The annual migration of India's government to Simla, the departure of Congress and officialdom generally from Washington with the advent of Summer, and the mid-day suspension of business now customary in hot climates are examples of habits that may be abandoned when manufactured weather becomes the rule in both private and public buildings.

Weather's Role In Human Affairs

One may, indeed, speculate upon much more remarkable effects of man-controlled indoor weather upon the future of the human race, implied in the well-known fact that man's physique and mentality are both influenced decidedly by his atmospheric environment. The time is not near at hand, however, when this environment can be artificially regulated on so general a scale that hot climates and the ultra-tropical hot spells of nominally temperate climates will cease to play despotic roles in human affairs.

The despotism of hot weather is illustrated every Summer in our own country. The Summer hot wave-popularly and sometimes officially so called, though the meticulous meteorologist is more inclined to describe it as a "heated term"-is all too familiar to the vast majority of American citizens. Inhabited localities entirely exempt from such visitations are almost, but not quite-unknown in the United States. Eureka, on the northern coast of California, is in this respect a luaus naturae among American towns, with its enviable record of having never experienced a shade temperature higher than 85 degrees Fahrenheit since regular weather observations began there more than forty-six years ago.

Effect on the Country

The ordinary American knows excesses of heat through frequent personal encounters with them, but he has only a vague and inadequate conception of what they do to the country at large. He thinks of them as a source of much discomfort and occasional mortality, but he does not realize that they often rank among the major disasters of atmospheric origin, surpassing in their injurious effects the most violent storms.

A general hot wave, with its blighting and death-dealing temperatures, leaves a trail of havoc that can be only partly estimated in terms of money. Among the effects that can be thus assessed are those it exercises on growing crops, and they sometimes make startling figures. Thus during a hot spell of 1894 the agricultural losses in the single State of Iowa amounted to more than $50,000,000, which was more than double the property loss inflicted by the famous Galveston hurricane of 1900.

Of the staple crops of the country corn and cotton are most liable to damage from overheating. In most cases droughty weather accompanying the hot spell is partly responsible for its effects on vegetation, but the cooking effect of the sun and of an intensely heated atmosphere is the cause of much irretrievable damage. When affected by drought alone, most crops will rapidly revive if favorable weather follows within a reasonable time, but once the vitality of the plant is destroyed by excessive heat no amount of properly distributed rainfall can repair the injury.

Conservative farmers in the West estimate that during a Summer of average warmth the damage resulting from occasional periods of high temperature, lasting from three to six days or more, reduces the yield fully 20 per cent.

Some idea of the direct effects of these visitations on human beings may be gained from the fact that during the heated term of August, 1896, 2,036 deaths from sunstroke were reported in the United States in three weeks. The actual number was probably much greater. In the hot spell of June 28 to July 4, 1901, upward of 700 people and more than 1,000 horses died of heat in New York City alone. It appears, however, that heat prostrations are by no means so frequent in American cities today during hot weather of given intensity as they were a generation ago; a change plausibly attributable, at least in part, to the introduction of automobiles.

An interesting train of economic effects accompanies any prolonged hot wave," wrote the late Professor Robert De C. Ward, and he has set forth a number of remarkable illustrations drawn from the history of the heat and drought of July, 1901, in the United States. Some of these effects, much more surprising than the stimulation of travel and of trade in hot-weather goods, are thus described:

"In order to save themselves the discomfort of shopping, customers sent in their orders by mail, and the large city stores were unable in many cases to keep up with their correspondence and had to engage extra clerks to handle it. The stock markets responded in a very striking way to the weather conditions. Not only were the prices of wheat, corn and other cereals markedly affected but so also were the stocks of the great cereal-carrying railroads. So sensitive to weather conditions are the stock markets that the prospect of even light showers in any portion of the hot-wave area was immediately reflected in higher quotations.

Effect on Produce Markets

"The lack of water and of pasturage and the inevitable future high price of corn led Western cattle men to ship their cattle to market in immense numbers. There was a greatly decreased market demand for meat and an increased demand for fresh vegetables, so great that the supply was wholly inadequate, and in many cities the available stocks of canned vegetables were sold out to meet the needs of customers.

"The settlement of a strike in some of the Pennsylvania steel mills was delayed because the operatives did not want to go back to work as long as the terrific heat lasted. In many cases manufacturing and industrial plants shut down and large wholesale and retail concerns in the cities shortened the hours of work in order to give their employees a rest."

Such were a few of the consequences traced to a typical spell of hot weather, and doubtless a host of others remained unrecorded. Statistics of weather effects are necessarily fragmentary. There are none, for example, to tell us how many students fail in examinations on account of inopportune hot spells, or how many juries cut short their deliberations because of intolerable heat in jury rooms. Hot Weather and Quarrels

Hot weather notoriously incites to quarrels. The tragic events of "Romeo and Juliet" all hinge upon the fact that Benvollo's prudent advice is unheeded:

I pray thee, good Mercutio, let's retire;
The day is hot, the Capulets abroad,
And if we meet, we shall not 'scape' a brawl.
For now, these hot days, is the mad blood stirring.

Professor E.G. Dexter was inspired by this Shakespearean example to study the relationship of brawls to temperature in New York City. He found that cases of assault and battery recorded on police blotters were 68 per cent above normal for men and 100 per cent above normal for women when the mean daily temperature was between 81 and 85 degrees, i.e., on days when the mercury crept well into the nineties in the afternoon and remained above 70 degrees at night. For still higher temperatures, however, the record shows a marked falling off in these hostile encounters. When the daily maximum is 100 degrees or more the angry spirit may be willing but the flesh is weak, and the patrol wagon is seldom called for.

The condition of affairs that we describe as "hot weather" is really a complex of several physical factors, and the conventional method of recording its intensity in terms of the temperature scale is far from satisfactory. The weatherman measures the temperature of the air with a shaded and screened thermometer, because it cannot be measured accurately in any other way. The thermometer acquires by conduction the temperature of the air in the screen, which is substantially the same as that of the air outside, and it registers this temperature. If exposed to sunshine or to radiation from heated objects it would no longer register the temperature of the air but merely that of the instrument itself, which in strong sunshine might easily be 40 or 50 degrees higher than the air temperature.

Thus meteorologists tell us how hot the air gets during a hot spell, but their records give us no definite idea of how hot human beings, animals, plants, pavements and various other things become in such weather.

Some Effects of Hot Spells

Some of the most striking physical effects of hot spells are due to the intensity of the sun's rays falling upon objects that, because they are surrounded by hot air, do not readily get rid of the heat they acquire by absorbing solar radiation. It is chiefly intense sunshine rather than hot air that causes apples to bake on the sunward side of trees, asphalt pavements to soften and steel drawbridges to expand.

Human sensations of temperature are still another story, since they are affected by air temperature, radiation from the sun and terrestrial objects, humidity and wind; and widely different combinations of these external factors produce the same feeling of warmth or coolness. Even the layman is familiar with the fact that hot, dry air feels cooler than humid air of the same temperature.

An electric fan does not cool the air, but it cools human beings by carrying away excessive heat from their bodies and also by promoting the evaporation of sweat, which is a cooling process. Low atmospheric humidity likewise tends to cool us by promoting evaporation.

The occurrence of heat stroke, including sunstroke, beats so little relation to thermometer readings that a few decades ago some medical authorities suspected it to be an infectious disease. We now know, however, that its incidence hears a close relation to the cooling power of the air. Generally speaking, its occurrence is favored by hot sunshine, high humidity and stagnant air, though an intensely hot, dry wind notably the Simoon of Asiatic deserts, can cause fatal heat-stroke through the effect of temperature alone.