EDITOR'S TABLE. 



845 



thus formed would have the same vertical 

 rigidity as the existing compression arches, 

 and it is obvious that the lateral bracing 

 which is necessary for the tubes of the erect 

 arch could be dispensed with for the links of 

 the suspended arch. The question of anch- 

 orages is outside of the comparison. 



The popular misconception as to sus- 

 pension bridges is due to the many insuf- 

 ficiently stiffened structures of this kind. 

 No other bridge system can be built so im- 

 perfectly stiffened, and yet be safe, as the 

 suspension bridge. An erect arch bridge 

 built in the same manner would fall of its 

 own weight. 



Another popular and fashionable concep- 

 tion, but a misconception all the same, is as 

 to the merits of the cantilever bridge. Theo 

 retically and practically, the cantilever of all 

 bridge systems has the greatest deflections 

 and oscillations under passing loads, all 

 other things being equal, and therefore is the 

 least rigid system. It has, however, its p;ood 

 uses otherwise. Gustav Lindenthal. 



PiTTSBtrBG, Pa., February 2, 1890. 



THE SALT PRODUCT OF KANSAS. 

 Editor Popular Science Monthly : 



Dear Sir: In your issue of January, 

 1890, page 430, under "Notes," it is said, 

 " One hundred and fifty-five barrels of salt 



were manufactured in Kansas in 1888, and 

 it is estimated that the output in 1889 will 

 be not less than three times as large." 



From the annual report of the Secretary 

 of the State Board of Agriculture for 1S88, 

 it is learned that seven salt-works reporting 

 produced 122,420 barrels. Of the seven, 

 three reported to December 31st, and four 

 to November 30th. One of the seven report- 

 ing began March 1 5th, three in October, and 

 two in November. 



From the same source for 18S9, 547,224 

 barrels of salt were manufactured and 19,- 

 056 tons of salt not put in barrels. Seven- 

 teen companies reported in the latter year. 



I have bought a copy of " The Popular 

 Science Monthly " since its first publication, 

 and I was loath to pass such an error un- 

 challenged. Success to you and yours. 



J. G. Wood. 



Topeka, Kansas, February 11, 1S90. 



[The number intended was 1 55,000 bar- 

 rels. The dropping out of the thousands in 

 transcribing the item escaped notice. On 

 the basis of that number, the output of Kan- 

 sas salt in 1889 would be, according to Mr. 

 Hay's estimate, not less than 465,000 barrels. 

 We thank our correspondent for giving us 

 the opportunity of correcting the error. 

 Editor.] 



EDITOR'S TABLE. 



POLITICAL ECONOMY. 



AMONG the regularly constituted 

 sciences that claim the attention 

 of the world to-day, it can scarcely be 

 said that political economy has an undis- 

 puted place. Fourteen years ago, in an 

 article on the centenary of the " Wealth 

 of Nations " (which fell in the same year 

 as the centenary of our Declaration of 

 Independence), the late Prof. Jevons 

 acknowledged that there was then far 

 less agreement among teachers of politi- 

 cal economy, in regard to the funda- 

 mentals of their subject, than there had 

 been fifty years earlier. He acknowl- 

 edged, also, how little interest was taken 

 in lectures on political economy at the 

 universities, and how little weight was 

 attached by practical men to proposi- 

 tions or principles put forth as the re- 

 sult of studies in that field. Row does 

 the matter stand now that fourteen years 



more have flown? Has the credit of 

 the economists of the generation that 

 has passed away the Mills, the Mc- 

 Cullochs, the Seniors, the Says been 

 in any degree rehabilitated? Scarcely. 

 As time goes on, it becomes increasingly 

 clear that the whole work of these writ- 

 ers was carried on too much in the re- 

 gion of abstractions, and was too little 

 vivified by direct contact with facts. 

 Bacon long ago remarked on the error 

 of those who supposed in nature a greater 

 simplicity than really exists; and this 

 error was abundantly exemplified by 

 the classical or "orthodox" economists. 

 It was to certain minds, no doubt, a fas- 

 cinating pursuit to seize upon two or 

 three general principles, and by their 

 help to interpret and methodize all the 

 complex phenomena of economic pro- 

 duction, distribution, and exchange; 

 but the process was hazardous in the 



