366 NATURAL SCIENCE [June 



various external conditions might permit. Dairymen had au idea 

 of the proper course to pursue under the special circumstances of 

 their locality ; but they worked blindfolded, and their calculations 

 were liable to be upset by unregarded variations of environment. 

 Dr Olsen has changed all this. He has investigated various 

 cheeses, and has caught and cultivated their microbes ; then he 

 has reversed the process, and used his cultures to produce the 

 various cheeses from which he started. The kinds of microbes 

 are not many, but by their combinations in different propor- 

 tions, different results are obtained. First there are the common 

 fermentation-microbes, common to all cheese, but replaceable, as 

 Babcock & Eussell have shown, by unorganised ferments. Then 

 come the species that affect the diagnostic characters of the future 

 cheese, its peculiar taste and smell. Cheesemaking now goes by the 

 card. The milk is sterilised and heated to 70°-75° C, and the 

 store-room is kept guarded against foreign microbes. Those that 

 are desired are added in the requisite proportions, and their vigor- 

 ous growth is of itself enough to overcome the influence of accidental 

 strays. The production of the kinds of cheese is no longer an affair 

 of the laboratory ; but Dr Olsen will take your order for Gorgonzola, 

 Stilton, or Camembert, and will furnish the precise description re- 

 quired at a cost satisfactory to your pocket and to his own. Nor- 

 way is a land specially adapted to the industry of cheesemaking, and 

 as Norwegian prophets differ from those of other countries in secur- 

 ing the hearty recognition of their countrymen, there is no doubt 

 that Dr Olsen's discoveries will be rapidly taken up in practice. 

 We wish therefore to draw the attention of tlie British farmer to 

 them without delay. 



Fishy Water 



We referred in our last number to a paper by Messrs Jackson & 

 Ellms on " Odours and Tastes of Surface Waters." We learn from 

 The Plant World that the city of Brooklyn, N.Y., has had much 

 trouble with its drinking water, complaint being made, especially 

 during the summer months, of its objectionable appearance, strong 

 oily taste, and what Trinculo would have called its " very ancient 

 and fish-like smell." The causes of this condition have been investi- 

 gated by Professor Leeds, of the Stevens Institute of Technology. 

 He finds that the whole trouble is due to the presence, in immense 

 numbers, of a diatom, Asterionella flavor. In some samples of water 

 as many as twenty million individuals to the gallon were found. 

 " Think of it ; drink of it then if you can." This diatom is 

 enclosed in the usual silicious skeleton, and has the power of 

 secreting a substance in the nature of an oil, which possesses the 



