6i6 THE POPULAR SCIENCE MONTHLY. 



city on the list is Sioux City, Iowa, and the next is Dulutli, Minn., 

 the expense being in the first $23.91 and in the second $23.08; but 

 this great expense is probably due to the extensive construction 

 of streets in a recent period, and therefore the expense of these 

 two cities should not be compared with that of others. Throw- 

 ing out the cities with abnormal conditions, it is probable that 

 San Francisco is the highest cost city in the list of fifty given 

 in the table, the expense being $11.41 per capita. 



The table will be found interesting in many respects, as com- 

 parisons can easily be made for one city with another, not only as 

 to total per capita cost, but as to the items enumerated. Looking 

 at the city of New York, for instance, the table means that it 

 would cost a family of five $35.25 per annum for the benefits ac- 

 cruing to it from -the use of streets and the cleaning thereof, 

 for public lighting, for the maintenance and repairs of sewers, for 

 police protection, for the protection of the fire department, and for 

 the use of water. No one can object to an expense for a family of 

 five persons no higher than that named for all these great advan- 

 tages. The working-man with five in his family is not taxed this 

 $35.25 directly, as intimated, but he has to pay it in rent and the 

 cost of his living. Is it an unreasonable addition to his an- 

 nual expenses ? is the question. It does not matter whether the 

 total expense is high or low for all the advantages detailed ; the 

 great question is. Could they be furnished as efficiently and 

 as well in every respect for a less sum, with the integrity of 

 all departments preserved ? If they could, then a man is entitled 

 to the less expense. If not, he should certainly be entirely 

 satisfied with the great return which he now gets for the money 

 expended. 



WAYSIDE OPTICS. 



By CASEY A. WOOD, C. M., M. D., 



mSTBUCTOR IN OPHTHALMOLOGY, CHICAGO POST-GRADCATE MEDICAL SCHOOL. 



OUR train has been traveling for the past twenty-four hours 

 over that part of a transatlantic route which stretches from 

 the Sierra Madre to the extreme borders of the great Mohave 

 Desert. There are many interesting things to be seen along this 

 line of travel, but nothing more striking than the curious optical 

 phenomena presented by the pleasing alternation of vast plain 

 with rugged mountain. For example, not far from the last station 

 we come upon a lofty peak overtopping the surrounding hills. It 

 seemed to be about ten miles away, but was in reality fifty. 



As is well known to the student of optics, the apparent size of 

 an object is mainly dependent upon the size of the image which 



