suited only to the determinatlon of high colors. Thin glass, of the same composition, might be made to satisfy all necessities of the case. The standard slip of glass is marked with a diamond, and the simultaneous use of a bundle of slips, of different values, permits the accumulation of any desired degree of intensity in color.

ON COLORS FOR SALT-GLAZED POTTERY. By A. A. BRENEMAN, of Ithaca, N. Y.

IN continuation of some experiments, reported at the last meeting of this Association, I have succeeded in obtaining in the ordinary stone-ware kiln, all of the colors shown upon the experimental tile here shown with many other tints and shades, not heretofore produced, to my knowledge, on this kind of ware. I have little doubt that a complete palette of colors may be obtained for the decorator in this field. The number of experiments made is so great, and the results are so various, that I shall not attempt a description of them at this time, confining myself for the present to a statement of a theory of the action of the saltglaze in its relation to mineral colors. This I believe, to depend upon a circulation by convection currents in the thin layer of sodium silicate resting upon the ware, after salt has been thrown into the kiln. As chlorine can have little affinity for the silicious matter of the glaze, while it is capable of volatilizing many of the metals which, in one form or another, are used as pigments, it would seem that the destruction of color, well known in the case of ordinary pigments, may be prevented by giving such consistency to the color-holding medium, that convection currents shall be impossible, at the temperature of the kiln; while at the same time this medium shall have mobility sufficient to permit of that migration of molecules, necessary to a uniform distribution of the color. Upon this theory my results have been obtained.

ON THE DEFICIENCIES OF METEOROLOGICAL WORK IN DATA OF VALUE TO AGRICULTURE, AND MEANS FOR SUPPLYING THEM. By WM. MCMURTRIE, of Washington, D. C.

WHAT I mean by deficiencies of meteorological work in this connection is the want of data in the published records, concerning many of those conditions recognized by agriculturists and vegetable physiologists, to have an important influence upon the normal development of animal and vegetable life; and that the observations of the present time are not such as will supply all the data required in the study of meteorology, in its relations to agriculture, and especially to the condition of the crops. The want of such data, I felt most keenly in my work of last year, a portion of the results of which I had the honor to present to the association, at the Saratoga meeting. In that work, the object was to determine the limits to the conditions to which the crop in question might be subject, and reach such development as would give a profitable return to producer and consumer; and while the results obtained were interesting to me at least, it was difficult to make them so thoroughly marked as would have been possible, if more complete data, such as I will mention later on, had been obtainable.

The records published give detailed data concerning barometric pressures, temperatures observed in the shade, rainfall, relative humidity, direction and force of the wind and conditions of the sky, expressed in percentages of cloudiness, and these are valuable in their way, and for the end to which the observations were taken but they by no means cover all that must be recognized in scientific and practical agriculture. Radiated as well as diffused heat, diurnal and monthly distribution of rainfall, evaporation of moisture, prevalence of dews, fogs and frosts, and tension of atmospheric electricity are also important and necessary. Light, that most patent factor in vegetable development, has been almost wholly neglected, except in the record of the condition of the sky, as expressed in percentage of cloudiness, which, in this connection. is as much a matter of accident as design.

Practical agriculturists have almost completely ignored the science of meteorology in the prosecution of their labors, repeatedly making attempts at the introduction of new crops into sections wholly unsuited to them on account of climate; and on the other hand, in the work of meteorologists, although agriculture

has been thought of and mentioned, the facts they have recorded have been collected more for the benefit of commerce than agriculture, and in the latter connection, they are, as we have said, sadly deficient.

Count de Gasparin seems to have been the first to call attention to the relations we have mentioned, and he has had at least two active followers, Quetelet in Belgium, and Marié-Davy in France. The sentiments of the latter in this particular are ably embodied in the prelude to an article in the Journal d'Agriculture Pratique of last year, in which he says, "Agriculture and its products have thus far received comparatively little profit from the labors of meteorologists, because the latter have been more preoccupied with questions of climatology in general, than with agricultural climatology, and the data they discuss, look to the first and not to the second." This difficulty belongs to all countries alike-Davy himself is making an excellent start in the right direction, at the Observatory of Montsouris, and he has already secured results of great scientific and practical value; but in order that his plan of work may be attended with the most fruitful results, he should have more extended coöperation, and the observations he makes and records should be made at a large number of stations, to render accurate generalization possible. -IIe observes and records all the conditions we have named. In this country, we have nothing comparable with it.

Our Signal Bureau, probably the most perfect of its kind, for the purposes for which it was designed, renders excellent service to agriculture and commerce, and we would not question its efficiency; but its work, as it claims, tends to the commercial rather than to the physiological side-to predictions of future conditions which may affect human affairs, rather than to the record and discussion of the effects of conditions which have existed, upon the development of crops. Nor is its organization sufficiently extensive to effect the end we have in view, the whole number of observers engaged under its direction, not being more than 800; while for practical deductions, for agricultural work, 3000 for the United States would not be excessive. But I believe the machinery and organization of the Department of Agriculture could be employed with good effect in this connection, and the desired observations for this country secured, through the 2300 observers and reporters it already employs to make monthly returns concerning

the condition of the crops, and who receive, as compensation for their services, the publications of the Department. If the necessary instruments were supplied them, it would doubtless be found that very few would decline to perform the tasks requested at their hands-making the observations and reporting weekly or monthly records to the Department, where their results could be tabulated and discussed in connection with their simultaneous returns of the condition of the crops.

I have, therefore, taken the liberty to suggest to Gen. Le Duc, the Commissioner of Agriculture, the following plan of work in Agricultural Meteorology for his Department, and I am pleased to say that he fully recognizes its necessity, and is in full sympathy with it, though he would, of course, require congressional support to enable him to carry it out.

1. The establishment of a system of observation and record among the reporters to the Department, and others whose coöperation may be secured throughout the United States and Territorics, with instruction to observers to keep careful records of the conditions of atmospheric pressure, temperature in its various relations, relative humidity, evaporation of moisture, winds, light, tension of atmospheric electricity, occurrence of dews, fogs, and frosts, and report them at stated intervals of time to the Department for consideration and permanent record.

2. The collection of meteorological records from every part of the world, from which to construct detailed tables, showing the relations of all the conditions named above, and that may influence the growth or health of vegetation.

3. The construction of maps showing the geographical distribution of various crops to be used in connection with the meteorological or climatic data to be collected.

To secure the data from abroad for this work, correspondence should be established with ministries of agriculture of foreign governments, learned societies, institutions of learning and research, and students in meteorology and allied sciences, requesting information concerning the published and manuscript records of each country and sources from which copies of them can be obtained. They should then be secured to facilitate the end in view. Information should also be requested concerning the cultures to which each country is devoted, those which succeed

well and are profitable, and those which have been experimented upon with unprofitable financial results.

In the tables and maps that could be constructed from the information thus gained, there would be found an almost perfect guide as to experiments that may be made in new cultures with prospect of success. Such work would in no way interfere with that of the Signal Bureau, the value of which cannot be overrated—and on account of the very nature of the work, it should be carried on by the Department of Agriculture. It would become an additional source of knowledge concerning that science in which all classes of the people are equally interested, and if the knowledge thus gained be applied to the management of farm crops, it will be difficult to estimate the saving that must result in the expenditure of time and means, and of enterprising and intelligent labor of agriculturists often employed in unfruitful experiments that could be directed to other channels of industry, or other and profitable cultures.

THE ACTION OF SUNLIGHT ON GLASS. BY THOMAS GAFFIELd, of Boston, Mass.

WHEN God made the light, He created one of the most ethereal and yet most powerful of the elements and forces of nature.

It will be my pleasure to show how the sun, its great fountain and source, while it paints so beautifully and wonderfully the birds, the insects and the flowers, can in some measure also delicately tint the wares upon our tables, the glass in our houses, and the windows of the storied cathedrals of the world.

My subject is the action of sunlight in changing the color of glass, and I shall give a brief account of my humble experiments, commenced in 1863, and continued to the present day.

There is no mention of the subject in ancient records, for there was little need or use of glass windows in the olden time, and probably little or no glass of composition or color liable to any very perceptible change of tint. Not until after the beginning of the present century was the phenomenon observed in Europe, in the change of some light colored plate glass to a purple and of