144 



THE POPULAR SCIENCE MONTHLY 



An Alley near the Main Street op 

 the Town. 



in a dwelling house, or elsewhere, may produce in the spring, at the 

 lowest estimate, one hundred and twenty eggs. Assuming that one 



half of these hatch as females, and 

 allowing that the breeding goes on 

 without check for four months, we 

 have as the descendants of a single 

 hibernating individual 214,557,- 

 S44,320,000,000,000,000flies. Now, 

 a house fly measures exactly one 

 fourth of an inch in length ; the 

 distance around the earth at the 

 equator is said to be 24,800 miles. 

 It would take, therefore 3,688,312,- 

 000 flies placed end to end to go 

 around the world once. Using this 

 number as a denominator, and the 

 number of flies produced in four 

 months from one mother as a nu- 

 merator, we find she will give rise, 

 in the course of a summer, to 

 enough flies to encircle the globe at the equator five thousand times, 

 and have plenty of progeny to spare ! 



In considering the relation of the house fly to typhoid, the question 

 as to how far a fly can travel may 

 suggest itself as an important fac- 

 tor, as, indeed, it is. We can not 

 speak definitely as to how far a 

 house fly can go by its own unaided 

 effort. It is evident, however, that 

 by making a series of flights this 

 insect could cover a considerable 

 distance. It does not, however, 

 have to depend upon its own pow- 

 ers for getting from place to place ; 

 railroad and street cars, carriages 

 and automobiles, provision wagons, 

 meat carts, horses, cows and other 

 animals all do their part in carry- 

 ing this pest free of charge. 



Turning once more to the con- 

 sideration of conditions on the Iron Eange we should naturally expect 

 to have found typhoid most rampant among the most filthy of the three 

 nations represented, but, strangely enough, such was not the case, for 



Virginia, Min. 

 In an out-house in the background the 

 excreta from a typhoid patient were de- 

 posited. The water in this pond was 

 used at that time by some of the neigh- 

 bors for washing. 



