SCIENTIFIC.

Otago Witness, Issue 1640, 28 April 1883, Page 28

SCIENTIFIC.

Atmospheric Dust and Disease Germs.

At a meeting of the Miscro'scopical Society in March of the present year, Mr H. S. Hanks read an interesting paper on "Some Notable Features of the great San Francisco Snow-storm of December 31st 1883." We give the following abridged account of thd address : — i In the course of his remarks Mr Hanks said that a snow storm at San Francisco, where such phenomena are almost unknown, r aturally becomes the absorbing topic of conversation out when the warm air dissipated the suowj it became a thing of the past and was forgotten. To the speaker, however, there was a certain feature connected with it, botli interesting and impoitant, to which his attention was called by .iccidenb. When the snow was falling ap-ptir-ntly clear and white, the idea occurred to h m that it offered an opportunity to obtain, without much trouble or libour, a stock of pure water for chemical purposes. After melting some in a tin vessel in his private laboratory, to his surprise lie found the resulting water quite milky, and a deposit or r<jbidue of a muddy character remaining in the can. Without attaching importance to the circumstance he proceeded to filter the water, but found the filterate still milky. Thinking the matter over he determined to examine the residue under |tho microscope, when he found he had in the field of the instrument finely divided sand. With thre clue he submitted the fine snow to a closer examination — mechanical, chemical, and optical. Uuder the microscope the .dv.st was ueen to be composed of rounded particles of quartz, with minute scales of mica, or jeffersite, and a large quantity of organic matter, principally vegetable fibre. On being calcined in a platinum dish, it at first burned, then blackened, and, on continuing the heat to incine»ation, the mineral portion only remained, mc uding a small ash. On cooling the loss was found to be 18 per cent, ind^pendant of moisture. While making experiments a " mud shower " occurred at Fresno, which covered everything with a coating of grey, sandy mud. Tha substance was the same as that found in San Francisco, the only difference btsing that the particles were a litttle larger, and the • vegetable fibre more abundant. At the same time snow which fell at Modesto was discoloured. It was the first snow at the place for ten years. The Modesto sand sample was found to be of the same general character, but the particles were larger than the others mentioned and tho organic matter was less, as follows ; Organic matter .. .. ..14 4 percent r/irguat partiules „. .. .. 0.19 v c'.'gh Smalltst jiartic'cs . . . . . . 0 001 inches The lecturer then wont on to show that the cause ot this substance in the atmosphere was the snow storms arising from the Californian deserts. He said stately columns of dust move slowly and majestically across the plains until they are dashed against ihe mountain.'! or become dissipated in the upper air, and the finer particles of the du-ty sand rise to a very great height,andbi comolo-ittos-ightlikooloudsofmisfc. Uust from the deso-ts of Africa has frequently fallen on the decks of ships iv the Indian Ocean and the Red Sea ; and on the summits of ,the highest acopssible mountains, on the snow and even on the bare rocke, dust has besn obeeryed which has been called " star

dust," " cosmical matter " and other similar names. Mr Hanks then drew atention to the poi.son contained in the. atmosphere, and said : "This subject becomes important when it is considered that the dust I have examined contained so large a quantity of organic matter, of which, without much doubt, a considerable part was in the form of germs. May it not be that the sudden and otherwise unaccountable appearance of strange plants, fungi, and low forms of vegetable life, and perhaps diseases, may be due to this cause. It is well known that on the most arid portions of the Colorado Desert, when accidentally irrigated by the overflow of the river, a dense and luxuriant growth of vegetation springs up from seeda and germs which must have lain dormant for many years. Certain localities in California have become unhealthy on the introduction of water for mining purposes or irrigation, and in many cases the country, before healthy, has become almost uninhabitable from this cause. May not the same effect be produced by germs, brought by the-winds ? I leave the answers to these questions to members of our Society who have made a special study of disease germs and will conclude with a calculation I have made of the quantity of dust that fell in San Francisco, based on the weight obtained and quantity of snow, as found in my experiments. Mr Hanks then made a rough approximate calculation of the weight of dust in the snow, as follows :—": — " Without going into details, my calculation gives seventy-live tons to the square mile, supposing the fall to have been uniform." He then concluded as follows : — "It is fair to assume that the upper air is frequently charged with dust, a oortion of which falls near the source, while a larger portion is carried to unknown localities, and that the falling snow on the occasion of the December storm gathered it together and deposited it in our streets, already surliciently dirty, verifying the proverb "to him that hath shall be given." Upon invitation, Dr Sternberg addressed the Society upon the points presented in Mr Hanks' paper. He said he had spent much time in microscopical examination of atmospheric dust both in Havana and New Orleans, where he was studying the yellow fever and its communication. Ho found in the air spores of fungi foreign to the locality, and which must have been brought great distances. This fact was also observed by Cunningham at Calcutta, India, Dr Sternberg found, also, pollen grains, which must have been blown from distant grain fluids ; also, pollen f i om pine forests which were fifty miles distant. Common air frequently contains, he said, starch granules and epithelial cells from the human skin ; also, fragments of cotton and wool fibre, &c. The first rain or fall of snow after a season of drought brings down all these matters from the air. In fact the first rain gives the sewage of the atmosphere. People using rain water should always reject the water which falls first, which contains the washing of the air and of the roofs, from which it is collected. Michel in Paris found the air loaded with germs of many kinds. He also found that tilth diseases are most prevalent when the air contains most of these germs. But by all these air studies conducted even in the time of plagues, there has been no discovery wh.ich would connect certain diseases with any certain germ. There are, however, diseases, as, for example, anthrax, which is known to be propagated by a germ, but it ha 1 ? not been recognised in the air. A United States army surgeon has written on the occurrence of fever in mountain distiicts, which was apparently caused by the blowing of malarial germs from the lowlands, and introduced into the system by rain water. STet these matters have not been recognised by collection of atmosuheric dust.