REPORT OF THE SPECIAL COMMITTEE ON OZONE AND OTHER ATMOSPHERIC CONDITIONS IN CONNECTION WITH RECORDS OF THE PREVALENCE OF DISEASES. MAY, 1881.

YOUR Committee respectfully submit the following report:At the annual meeting of the Association in Buffalo, 1878, on the motion of Dr. JAMES P. WHITE the following resolution was adopted: "Resolved, That a committee of five be appointed to confer with General Meyer upon the subject of making observations as to the existence of ozone in various localities, and take such other steps and measures as may be necessary for the success of the object."

The committee appointed under this resolution entered into correspondence with General Meyer, for the purpose of ascertaining whether he, as Superintendent of the Signal Service Bureau of the general government, could not be induced to add observation on the electric and ozonic conditions of the atmosphere to the meteorological conditions already recorded, at certain selected stations in charge of the agents of that service.

The superintendent, however, was found not willing to attempt the making and recording of such additional observations, until the committee, or the Association it represented, could point out more definitely the best methods for making the observations proposed and the best instruments required for the purpose. At the next annual meeting of the Association, which was held in Atlanta, May, 1879, the Committee made a brief report,' stating the foregoing facts in regard to their correspondence with General Meyer, accompanied by some suggestions concerning the great importance of obtaining reliable parallel records concerning all appreciable conditions of the atmosphere, and the date of attacks of all acute diseases, through a series of years, in several localities. The report further suggested that the Association test the practicability of the work, by causing

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a limited number of localities to be selected, in each of which a properly qualified physician should be selected and furnished with the necessary instruments to observe and record, daily, the atmospheric conditions, and a number of others, engaged in active general practice, to record the date of the commencement of attacks of all acute diseases coming under their observations; both parties to report to a committee of this Association the results of their observations at stated periods. The Committee closed their report with a resolution, which was adopted by the Association, as follows: "Resolved, That a committee of five be appointed by the President, whose duty it shall be to investigate the practicability of carrying into active operation the foregoing plan of observations, the cost of the instruments and means required, the twelve best localities in which to begin the work, and whether the required number of qualified observers can be secured in each, and report the same for the consideration of the Association at its next annual meeting."

The president appointed the undersigned as a committee under the foregoing resolution. The special work of the Committee was to investigate and report on the practicability of establishing two series of recorded observations, running parallel with each other in the same localities, through several years. One series was to embrace a record, by a competent physician or scientist in each locality, of all known and recognizable qualities and constituents of the atmosphere; and the other was to embrace records of the commencement of attacks of acute diseases in the same localities, by a number of active and competent practitioners.

The object was to obtain reliable data through a series of years and in a sufficient number of places, by which an accurate comparison could be made between the prevalence of any given form of acute disease and the meteorological and other conditions of the atmosphere, in the hope of developing more exact knowledge of the etiology of many of the more important diseases, especially of an epidemic and endemic character.

The Committee were soon satisfied by the almost uniformly favorable answers to their inquiries, that there would be no difficulty in enlisting a sufficient number of active practitioners to keep the records of the prevalence of diseases; but to find competent men and reliable materials and instruments for carrying on the other branch of the inquiry, was a work of far more dif

ficulty. Indeed, the farther inquiries were prosecuted, the more did evidences accumulate, going to show not only that the tests instituted by Schönbein for determining the presence and quantity of ozone in the atmosphere were wholly unreliable; but also that there were just reasons for doubting whether the agent called ozone really had any existence as an ingredient in the atmosphere. It is true that since the first announcement of the discovery of ozone by Schönbein, many articles and monographs have been written concerning its properties, and its influence on the prevalence of certain diseases; and the word has become so familiar in etiological investigations and medical works, that only those who institute special inquiries or who read with au unusual degree of critical acumen, would detect the uncertainties that environ the whole subject.

Obviously, the first object to be accomplished by your Committee was to find some reliable method and means for ascertaining and recording the presence and quantity of ozone in the atmosphere at any given time and place; and the same in regard to free electricity. In pursuing this object, the chairman of your Committee has had free access to the very extensive collection of French, German, and other Continental medical works and periodicals in the library of Dr. J. S. Jewell, of Chicago, as well as to a wide range of English and American literature. The Secretary of the Michigan State Board of Health has kindly furnished us with, not only the interesting records in relation to ozone contained in the published transactions of that Board, but also the advanced sheets of more recent papers not yet published. We think we do not claim too much, therefore, when we say that our search for some reliable and practical tests for the presence and quantity of ozone and electricity in the atmosphere has been both extensive and diligent. And so far as relates to ozone as a distinct element of the atmosphere, we are compelled to accept the conclusion arrived at by Schöne in a recent elaborate paper upon the reactions hitherto relied on to prove the existence and relative quantity of ozone, namely, that at present we have no tests by which we can accomplish these objects with a reasonable degree of scientific accuracy. Ninetenths of all the recorded observations concerning atmospheric ozone, have been obtained by the use of test-paper prepared with potassium iodide and starch, as originally proposed by Schönbein. And yet it is now fully established that this paper

is so readily affected by atmospheric moisture, currents, temperature, light, chlorine, ammonia, etc., as to render the results wholly unreliable; and their further use in prosecuting etiological inquiries should be avoided. The modification of the potassium iodide test by substituting red litmus paper as used by Houseman, remedies only a part of the defects belonging to the more common test-paper. The same may be said concerning the tests founded on the use of manganese, sulphate of lead, tincture of guaiacum, and indigo. Schöne claims that properly prepared thallium paper affords a sufficiently delicate test for ozone, while it is not affected by moisture, light, ammonia, and other influences to which the iodized paper is amenable; but it is influenced in the same manner by the presence of hydrogen peroxide as by ozone. If this is true, and it be conceded that hydrogen peroxide is a constituent of the atmosphere, as first demonstrated by the same writer, it must also be conceded that no tests have yet been devised by which these two substances can be distinguished from each other as they exist in the atmosphere.

It has been claimed that pure metallic silver would show a peculiar change of color when exposed to an atmosphere containing ozone, and would, therefore, constitute a proper test. But Ory, in his paper on ozone in the New Dictionary of Practical Medicine and Surgery, adduces the results of experiments showing that silver is acted upon only when the ozone is present in considerable quantity; and Schöne, after directly exposing plates of pure silver to the air for several weeks near Moscow without any effect, says there is no proof that silver is blackened by exposure to the air unless sulphur be present.

If, however, we are thus compelled to acknowledge, that, in the present state of chemical and meteorological investigation, we have no reliable mode of determining the presence and relative quantity of ozone in the atmosphere, as distinct from hydrogen peroxide and other agents, it does not follow that all past labor in this direction has been without value.

On the contrary, such labor has resulted in fully establishing the important facts, first, that there is present in the atmosphere a variable quantity of some one or more very active oxidizing agents besides ordinary oxygen, whether such active oxidizers be hydrogen peroxide, allotropic oxygen, or ozone, or both; and second, that many of the tests hitherto relied upon are so readily

affected by heat, light, moisture, atmospheric currents, electricity, ammonia, etc., that their further use should be abandoned whenever results of scientific value are desired; and such tests only be substituted as will be influenced by active oxidizing agents with sufficient readiness without being modified by other variable or accidental elements in the atmosphere. If the facts adduced in the recent and elaborate papers of Ory, Eulers, and Schöne can be relied upon, the nearest approach to such a test is properly prepared thallium paper. For while this paper is influenced in the same manner by hydrogen peroxide and ozone, and, therefore, does not enable us to distinguish one of them from the other, yet as both are active oxidizers and reputed to produce very similar effects in the human system, the point of chief practical importance is to determine their aggregate amount rather than their separate existence. In other words, for etiological purposes the important object is to determine the presence and relative quantity of active oxidizers present in the atmosphere at given times and places, that we may compare such presence with the coincident presence and progress of diseases in the same localities. The mode of preparing and using the thallium paper will be found fully stated in the recent papers

of Schöne.

In regard to the practicability of registering accurately the presence and relative quantity or intensity of free electricity in the atmosphere and the best instruments for the purpose, your Committee will report very briefly. The status of atmospheric electricity is so readily influenced by heat, moisture, atmospheric currents, passing clouds, and even the proximity of trees, that the preservation of a reliable record has been found extremely difficult.

The electrometer and apparatus devised by Sir Wm. Thompson is generally regarded as the best in use; and yet it appears to be generally conceded that this apparatus indicates the status of electricity in the surface of the earth, rather than that in the atmosphere. These circumstances, in connection with the expensiveness of the apparatus, have induced your Committee to recommend the abandonment of all efforts to make a record of atmospheric electricity for the present, and substitute in its place recorded observations in another and comparatively new field of much etiological and sanitary interest.

It has long been known that the atmosphere is liable to con