In the Geneva Archives dra science* for NoTeniber, ITieSl, Mr. Freuilei'icli Iias nn article upon the number of living organlsma in the air of the Swiss Alps. He ahowa that the experimeuta maile b; Poateiir iu 1800 upon the same subject, ami later by Tyndall, are unsatiBfactory becauiw of the small amount of air filtered, anil because It seems, from the results, lliat the germs were not deatroyed from the boiiUInn which was used in the esperiraent. Other observers bave found astonishing quantities of germa in high alti- tudes, and in all these cases It seems very probable tliat l.be liquid was not thoroughly aterilized.
In Freiiderlch'a eKperimente, by mesns of a port- able aleam-pnmp, a!r waa pumped at the rale of a bundrei] and titty litres an hour through a small glass ttihe with a capillary end. This tube was atoppcd with a wad o( spun elfl^s ^° retain any floating par- ticles. Each wad wa!4 then placed entire In the liouil- hm. Later be still further modified this method by using the tube throiigb nliicli the air was pumped as a ciiltn re-tube.
Mr. Freuderleli's most reliable experiments were made in the summers of 1S83 and 1884. On the 12tb of July, \m\ at the height of 3,200 metres. In 300 litres of air, no life was found. Again, on Aug. 5, at the height of 2,100 metres, he filtered SOD litres of air, and, on the next day, 400 litres on the summit of a neighboring mountain 3,!)70 metres high. The filterings from these two were sown iu a broth of beef, bnt showed no signs of life. At Schllthorn (2,(172 metres), Aug. 25, 1.600 liirei of air were fil- tered and sown, but ihe fluid did not cease to be limpid.
In presence of the negative results of ISS3, he de- termined not to confine himself in 1S34 lo the limit of eternal aiiow, but to choose some places more acces- sible to the germs of the air, On the Aletach glacier, July 15 and 17, at a height of 2,900 metres, he pumped 2,000 litres of air through six wada. One of the wads, after a rest of fifteen days, gave birth lo an orgsinUm of the family Tortuiacea, and another contained a micrococcus, which may have been ac- cidentally introduced. The second series was carried on above snow-level in Thcodule pass (:S,340 metres above sea-level) on the 6th and Tth of September. But in :i,000 litres of air he could find but one bac- terium. The extreme poverty of the air at these heights ia sufficiently proved by these figures. While these experiments were going on, the days were clear bnd the wind light, both circumstances favorable to the growth of microbes.
At Niesen (2,360 metres), July 26 and 211, rain and •now fell, and rendered the work very complicated, soaking the wads, and checking the work, so that not more than flOO litrea were pumped through eight wads, all of which were sown at Berne, July 27. On July 2i< the licjuias sown with two of them were in- fested with a peculiar long bacillus, never met with except in the air of Berne; the next day another was infetled with the fame species; a fourth gave another
��bacillus ; and Aug. 1 a mould appealed. Finally, about the first of September, a last conserve brought forth a mould after six weeks' incubation. The two others remained sterile; and hence we have a mini- mum of four microbes from 800 litres. We say minimum, because it ia possible that more than ono germ may have been caught on those filters which produced germs. Iu another trial, July 31 and Aug. I, he filtered 1,7^5 litres through fifteen wads, in which he found four bacteria. In reducing the le- sults, we find that we have in the air near Nleaen between three and four bacteria in a cubic metre.
The richness of the air In this region Is easily ex- plained by the locality, the mountain being sltualed on the border of Lake Thun, and surrounded by a number of towns. Besides this, a small amount uf vegetation is found on its summit. It seems that the purity of the air in these high altitudes is due less to the height than to the lack of a productive home for the growth of these organisms. From these ex- periments it aeema perfectly proper to conclude that the mountain air is much purer than that of the lower regions, and even more so than has been sup- posed. Indeed, It is surpassed in purity only by that over the sea, which Commander Moreau has shown to contain only five or six microbea to lea cubic
��RECENT PROGRESS IN ENGINEERING.
Sib Fhbiikrick Bkauwell, In his inaugural address as the recently inducted president of the Brit- ish Institution of civil engineers, called attention to the great progress made, during late years, in varlnus departments of engineering. Taking up, first, the materials of construction, he noted the enormous gain in the economy of brick-making by the intro- duction of brick-making machinea and the continu- ous kiln ; the improvement taking place in the making of artificial stones now enabling them to be produced with uniformity of quality, and of such ilurability as to constitute them successful rivals of natural stones. The use of wood is steadily decreas- ing, partly in consequence of its scarcity, and of its unfitness for use where longitudinal stresses are to be encountered, and partly through the introductiuii of the other materials, which are now made at less cost than formerly. Progress la to be expected in the direction of improved processes for the preser- vation of limber. Asbestos paint, as used on ihe buildings of the propused International inventions exhibition, has proved a safeguard In that case against fire.
The modern processes of steel manufacture are fur- nishing masses of enonnnus magnitude, and of great uniformiLy of quality. The proceeaes of Siemens and of Bessemer are now supplying such steels; while the method of Thomas and Gilchrist Is per- mitting the use of ores formerly quite Inapplicable lo such purposes. The cost of cast-iron is ilccrcoahig with the construction of larger furnaces, and the use of more highiy heat«d blast, and with a better understanding of the chemistry of llie process of
�� �
