There is probably an optimum temperature for thawing or defrosting frozen fruits and flowers. Finally the temperature records as ordinarily obtained need careful interpretation. It may be that the freezing point of liquids under pressure in the plant cells or exposed to the air through the stomata is not the same as in the free air. It is unfortunate too that in most places data showing temperatures of soil, plant and air are of doubtful character. A word of warning may be given against the too ready acceptance of Weather Bureau records made in cities and on the roofs of buildings. Garden and field conditions vary greatly from these. It is further advisable to obtain a continuous record of the temperature of evaporation such as is shown by the records herewith. The two temperature curves made simultaneously and easily read at any moment enable the gardener or orchardist to forecast the probable minimum temperature of the ensuing ten or twelve hours. But not always, and some study is necessary. A slight increase in cloudiness or a slight shift in wind direction will prevent the fall in temperature which otherwise seemed probable. With a persistent inversion of temperature there is sometimes an increasing absolute humidity.
SUMMARY
The problem is many sided and we must consider the motion of the air vertically as well as horizontally. Air gains and loses heat chiefly by convection, and any gain or loss by conduction may be neglected. The plant gains heat by convection, radiation and perhaps by conduction of an internal rather than surface character. The ground gains and loses heat chiefly by radiation. But the whole process is complicated and may not even be uniform. Frosts generally are preceded by a loss of heat from the lower air strata, due to convection and a horizontal translation of the air. Then follows an equally rapid and great loss of heat by free radiation. There are minor changes such as the setting free of heat in condensation and the utilization in evaporation, but these latent heats are of less importance than the actual transference of the air and vapor and the removal of the latter as an absorber and retainer of heat.
Frosts are recurrent phenomena reasonably certain to occur within given dates, and, as pointed out above, the cumulative losses are considerable. Methods of protection to be serviceable must be available for more than one occasion, for there is no profit in saving a crop on one night and losing it on the succeeding night. But the effort is worth while. Consider that the horticulturist regularly risks the labor of many months on the temperatures of a few hours. An efficient frost fighting device is in a way the entering wedge for solving problems of climate control. One may not take a crop indoors, it is true, but there is no valid reason, in the light of what has been already accomplished, why at critical periods which may be anticipated, the needed volume of surface air may not be sufficiently warmed; and the losses which have heretofore been considered inevitable be prevented.
THE PROGRESS OF SCIENCE
THE NEW YORK MEETING OF THE NATIONAL ACADEMY OF SCIENCES
THE National Academy of Sciences held its annual autumn meeting during the third week of November in the American Museum of Natural History. The central situation of New York City and its scientific attractions led to a large meeting and an excellent program There were present over sixty members, nearly one half of a membership widely scattered over the country. When the academy was established in 1863 as the adviser of the government in scientific questions, the membership was limited to fifty which was subsequently increased to 100, under which it was kept until recently. The present distribution of the 141 members among different institutions in which there are more than two is: Harvard, 19; Yale, 15; Chicago, 13; Johns Hopkins, 12; Columbia, 11; U. S. Geological Survey, 8; Carnegie Institution, 5; California, Rockefeller Institute, Smithsonian, 4; Clark, Wisconsin, Cornell, Stanford, 3.
The scientific program of the meeting began with a lecture by Professor Michael I. Pupin, of Columbia University, who described the work on aerial transmission of speech of which no authentic account has hitherto been made public. To Professor Pupin we owe the discovery through mathematical analysis and experimental work of the telephone relays which recently made speech by wire between New York City and San Francisco possible, and we now have an authoritative account of speaking across the land and sea a quarter way round the earth. One session of the academy was devoted to four papers of general interest. Professor Herbert S. Jennings, of the Johns Hopkins University, described experiments showing evolution in progress, and Professor John M. Coulter, of the University of Chicago, discussed the causes of evolution in plants Professor B. B. Boltwood made a report on the life of radium which may he regarded as a study of inorganic evolution. Professor Theodore Richards, of Harvard University, spoke of the investigations recently conducted in the Wolcott Gibbs Memorial Laboratory. These are in continuation of the work accomplished by Professor Richards in the determination of atomic weights, which led to the award to him of a Nobel prize, the third to be given for scientific work done in this country, the two previous awards having been to Professor Michelson, of the University of Chicago, in physics, and Dr. Carrel, of the Rockefeller Institute, in physiology.
Of more special papers, some of which, however, were of general and even popular interest, there were on the program 36, distributed somewhat unequally among the sections into which the academy is divided as follows: Mathematics, 0; Astronomy, 3; Physics and Engineering, 7; Chemistry, 1; Geology and Paleontology, 6; Botany, 7; Zoology and Animal Morphology, 8; Physiology and Pathology, 4; Anthropology and Psychology, 0. A program covering all the sciences belongs in a sense to the eighteenth rather than to the twentieth century; still there is human as well as scientific interest in listening to those who are leaders in the conduct of scientific work.
The academy was fortunate in meeting in the American Museum of Natural History, where in addition to the scientific sessions luncheon and an evening reception were provided. The museum has assumed leadership both in exhibits for the public and in the scientific research which it is accomplishing. The planning of museum exhibits is itself a kind of research and in this direction the American Museum, together with the National Museum in Washington and the Field Museum in Chicago, now surpasses any of the museums of the old world and in the course of the next ten years will have no rivals there. It is interesting that the city and an incorporated board of trustees are able to cooperate in the support of the museum, as is also the case with the Zoological Park and the Botanical Gardens which the members of the academy visited in the course of the meeting.