53G ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



mals. He considers that in every instance of the occurrence 

 of entozoa, whether in the form of trichina, hydatid, etc., the 



cause is directly traceable to the food we eat, the water we 

 drink, or the air we breathe ; and that it is probable that the 

 majority of cases originate from the first two causes. He 

 therefore urges that sewage matter should first be precipi- 

 tated and collected in the solid mass before being applied as 

 a fertilizer, thereby permitting the water thus purified to es- 

 cape into the ordinary drainage of the country, without in- 

 volving the terrible consequences referred to above. 20 A, 

 March 4, 253. 



PURIFICATION OF GYPSUM WATERS. 



The water of many springs and streams, otherwise com- 

 paratively useful, is found to contain so large a percentage 

 of gypsum as to render it unfit for ordinary purposes. Dr. 

 Reinsch informs us that if finely ground witherite, or native 

 carbonate of baryta, be added to the water in the proportion 

 of about half a pound to forty gallons, and the whole well 

 stirred together and allowed to settle, the suj^erincumbent 

 water will be found entirely free from gypsum, and to con- 

 tain only a slight percentage of carbonate of lime, which, as 

 is well known, when in a moderate quantity, is rather bene- 

 ficial than otherwise to the health. 8 C^June 23, 1870,197. 



TYNPALL OX THE PURITY OF WATER. 



Our readers will remember the interest excited by a lec- 

 ture given by Professor Tyndall before the Royal Institution 

 upon Dust and Disease, in which he presented some startling 

 facts as to the impurity of the atmosphere, and made some 

 important suggestions as to the method of improving the 

 quality of the air we breathe. 



The Professor has lately delivered a lecture upon the col- 

 or of water, and the scattering of light in water and in air, 

 which will probably be of equal practical value with that 

 first referred to. His subject was illustrated, as before, by 

 passing a beam of light through the liquid in a darkened 

 room, by means of which the existence of the minute parti- 

 cles of impurities can be readily detected. 



Lately engaged as one of the savans of the eclipse expedi- 

 tion, he embraced the opportunity to gather samples of wa- 



