ESSAYS ON THE FLOATING MATTER 

 OF THE AIR, 



JN RELATION TO PUTREFACTION AND INFECTION. 

 By Professor JOHN TYNDALL, F, R. S. 



ISmo. Cloth, Sl.SO. 



"Tyndall has lately considered what he calls ' the floating matter of the air,* and 

 has given many experiments and observations of his own, as well as those of Pasteur 

 and others, in regard to the g^erm theory of decay and disease. The volume before ua 

 does not come down later than the summer of 1881, but it indicates clearly enoug:h the 

 course that modem science has taken in regard to fermentation, putrefaction, and 

 contagious or epidemic diseases. In brief, tliis course is toward the establishment of 

 a distinctly vegetable or animal origin for all the developments of fermentation, pu- 

 trefaction, and contagion— this origin being found in the bacillus, the bacterium, or 

 other microscopic creature which reproduces itself with surprising readiness in all 

 possible situations where it can appear. Tyndall's gi*eat instrument of observation is 

 not the microscope- -though he makes use of that— but a concentrated benm of light, 

 passing t^ ^ugh the air, the chemical solution, the infusion of hay, turnip-seed, beef- 

 juice, or 1 . 'lor substance, with which he may may wish to experiment, and revealing 

 there, or failing to reveal, the obscure infusorial lite which his reseai-ches involve. He 

 appears to demonstrate that 'the individual particles of the finest floating matter of 

 the air lie beyond the present reach of the microscope,' while, as he adds, the con- 

 centrated beam of light 'reveals them collectively, long after the microscope has 

 ceased to distinguish them individually.^ lie thus has, as he believes, ^viitually a 

 new instrument, exceeding the microscope ludefiultely in power.' I'his will not at 

 lirst be admitted, and has in fact been denied, but the demonstratton seems to bo 

 with TyndalL His book will at once command attention.'' — Springjidd Mepublican. 



" To the wide-awake, common mind, a strong ray of sunlight shining through a 

 key-hole into the quietest and cleanest room will reveal pretty much all needed evi- 

 dence that most 'good air,* like 'pure water,' is very much alive, and that a clean 

 vacuum is not to be found. Professor Tyndall's bocik is a calm, patient, clear, and 

 thorough treatment of all the questions and conditions of nature and society involved 

 in this theme. The work is lucid and convincing, yet not prolix or pedantic, but pop- 

 ular and really enjoyable. It is worthy of patient and renewed study." — Philadelphia 

 Times. 



" The matter contained in this work is not only presented in a very interesting way, 

 but is of great value."— ^c?*toa Journal of Commerce. 



"The germ theory of disease is most intelligently presented, and indeed the whole 

 work is instinct with a high intellect."— Boston Commonwealth. 



"In the book before us we have the minute details of hundreds of observations on 

 infusions exposed to optically pure air ; infusions of mutton, beef, haddock, hay, turnip, 

 liver, hare, rabbit, grouse, pheasant, salmon, cod, etc.; infusions heated by boiling 

 water and by boiling oil, sometimes for a few moments and sometimes for several 

 hours, and, however varied the mode of procedure, the result was invariably the same. 

 with not even a shade of uncertainty. The fallacy of spontaneous generation and 

 the probability of the germ theory of disease seem to us the inference, and the only 

 inference, that can be drawn from the results of nearly ten thousand experiments per- 

 formed by Professor Tyndall within the last two ye^ne.''^— Pittsburg Tdegraph. 



For sale by all booksellers; or sent by mail, post-paid, on receipt of price. 



Hew York: D. APPLETON & CO., 1, 3, & 5 Bond Street. 



