26 D UST AND HAZE. 



the many organic constituents of dust which are 

 familiar to microscopical observers. Pouchet found 

 in the dust of the air (Comptes Rendus, March 2ist, 

 1859), " the detritus of the mineral crust of the earth, 

 animal and vegetable particles, and the minutely 

 divided debris of the various articles employed in our 

 wants." Mr. Samuelson, many years before 1863, 

 obtained living germs from dust taken from the 

 window panes, and from other common-place localities, 

 and gave numerous figures of the different forms he 

 discovered ("On the Source of Living Organisms," 

 Quarterly Journal of Science, Vol. I., p. 598). 

 Many other observers have also examined dust of 

 various kinds with great care, and have described 

 the organic particles existing in it in great numbers. 

 Yet in spite of the numerous observations which 

 have been made and published ^ upon this subject, we 

 find Dr. Tyndall teaching the public in a lecture on 

 " Dust and Haze!' given at the Royal Institution on 

 Feb. 1 8th, 1870, and afterwards published in several 

 newspapers, that he had only just discovered that the 

 dust of our air contained organic particles. His re- 

 marks were afterwards more widely diffused in several 

 journals under the title " Dust and Disease," no con- 

 nection whatever having been shown by the lecturer 

 to obtain between disease and dust or between either 

 and germs. Dust may certainly be perfectly harmless.* 



* Witness the cavalcade of picturesque stalwart women crossing Hyde 

 Park every evening on their way from the dust-heaps at Paddington, to 



