512 SUMMARY OF CURRENT RESEARCIIES RELATINQ TO 



at 2900 metres on the Aletscli gLxcior, a bacillus und micrococcus, a 

 mildew spore aiul tornla wore found ; omitting these last as not being 

 microbes properly so called, there was an average of 1 per cubic 

 metre. Out of 3000 litres taken at 3340 metres on the Col du 

 Theodule a Bacterium tenno and a mildew spore were found, or one 

 microbe per 3 cubic metres. On the Niescn out of GOO litres of air 

 taken during rain, snow, and intense fog a minimum of four microbes 

 (without counting mildew spores) was found. In a second trial out 

 of 1725 litres four bacteria were found. The abundance of microbes 

 here is explained by the fact that the observations were taken during 

 hay-making and by the presence of bacteria in the soil. 



Experiments made at lower levels were as follows : — Near the 

 Eggischhorn Hotel at 2193 metres above the sea, out of 110 litres a 

 PenicilUum and three species of Bacillus Avere found, or at least 

 SO germs per c. m. At Zermatt (1G20 metres) 100 litres gave a Bacillus 

 suhtilis and a mildew spore. A room in the hotel near the summit of 

 tlie Niescn gave an avei-agc of one bacillus to 7 litres of air. At 

 Gurten, near Bern, at an elevation of 323 metres above that town, 

 no germs were obtained : whilst at Bern itself 444 and 250 microbes 

 per cubic metre were taken. 



The conclusion drawn from the experiments is that the purity of 

 the air of mountains is much greater than has been supposed, and is 

 only surpassed by sea air. This purity is owing (1) to the progressive 

 disappearance of bacteria-producing centres ; at the zone of eternal 

 snow the absence of these centres is complete. 2. To the diminished 

 density of the atmosphere, which becomes less and less capable of 

 sustaining long in suspension the microbes it contains ; at the same 

 time the foreign particles arc more diluted by the very fact of this 

 decreased density, the space occupied by a given volume of air from 

 the plains augmenting with the altitude. 



MICKOSCOPY. 

 a. Instruments, Accessories, &c.* 



Beck's "Star" Microscope. — In the construction of this Micro- 

 scope (fig. 99) Messrs. Beck appear to have reduced the cost of an 

 efficient instrument to its very lowest limits, 31. 3s. only being charged 

 for it, including a 1 in. and 1/4 in. objective, which, it is claimed, 

 " are accurately worked, purely achromatic, and thoroughly suited for 

 scientific research." 



The Microscope is nickel-j)lated throughout, with the exception 

 of the base, which is solid in design, and contrived so that the instru- 

 ment is steady in every position. It is made in two forms, with a 

 sliding or a rack-and-piuiou coarse adjustment. 



* This siilxlivisiou is arranged in the following order: — (1) Stunds; (2) Eye- 

 piece and Ulgtctive; (3) lUumiuatiug Apparatus: (4) Other Accessories; 

 (5) Photo-micrography ; (6) Mauipulatiou ; (7) Microscopical Optics, Books, 

 and ]\Iiscellancous matters. 



