290 The Magnesium and Electric Ligld [*jouS,"unTmo.' 



application at any spot, the collection of the atmospheric particles 

 into a small space in such a manner as to he at once microscopically 

 examined Avith a ^Vth or -^Vth objective, placed on a growing shde, 

 or some form of cultivating apparatus for further observation, or 

 mounted permanently. The difficulty is to select the best culti- 

 vating medium. Hitherto I have found besides (debris) organic 

 and mineral matters, poUen grains, minute germs of various fungi 

 or protophytes, and excessively minute bodies, "molecules," "glo- 

 bules," &c. ; none were seen in motion. All seem to vary in 

 abundance with the force of the wind and dryness of the ground. 



This apparatus is deficient as regards crucial tests, but for 

 general use it is efficient, and may, by continued employment, be of 

 service. If any doubt exist as to the medium furnishing the spores, 

 it can be treated as though it bad been exposed; hence thus far 

 we have fairness in the results. 



I }3elieve it will be only by constant, varied, and multiplied 

 research, we shall ever obtam any answer to the important ques- 

 tion of " dust and disease ;" hence my excuse for trespassing on the 

 pages of this Journal, in the hope others may be induced to give the 

 apparatus a fair trial or suggest something more useful. 



P.S. — The examination of the collections made over forty days 

 has shown that in this immediate locality, at this period, the air 

 cannot be considered as loaded with microscopic germs ; the largest 

 number visible and counted as such on one cover being twenty- 

 one (not including bacteroid bodies). A few only have germinated ; 

 they are under observation. 



The photographs w^ere difficult to execute to secure the appear- 

 ance of the minutest granules, as many of the large particles of 

 sand, &c., were much out of correct focus; still I preferred this 

 method as more truthful than any hand drawing, especially for 

 Nos. 2 and 3. Some of the particles, which, under the low power 

 used to photograph them, appear in the })rints as " globules " — with 

 clear centres and dark outlines— with higher powers were found 

 very irregular in form. [The drawings in the Plate are selections 

 from some of Dr. Maddox's photographs. — Ed, M. M. J.] 



IV. — The Magnesium and Electric Light as apjilied to Photo- 

 micrography. By Brevet Lieutenant-Colonel J. J. Woodward, 

 U. S. Army. 



The following very interesting remarks constitute the report by 



Dr. "Woodward to the Sui'geon-General of the United States Army : — 



I have the honour to inform you that on the 25 th of October 



