76 



SCIENCE. 



[Vol. II., No. 24. 



of the falls, the other works of preservation 

 — the timber apron, the rolling dams above, 

 and the crib which had been placed below, 

 the falls — were described and commented 

 upon. 



Dr. C. E. Emerj- read a short paper, and 

 submitted a table, showing the cost of steam 

 engines and boilers complete, and the cost of 

 operating the same for three hundred and nine 

 days in the .year, including repairs and renew- 

 als, and giving, upon the data assumed, the 

 total cost per horse-power maintained continu- 

 ously. He pointed out why small engines 

 were comparatively more expensive to main- 

 tain than were large ones. The discussion of 

 this paper was postponed until the next day. 



The convention re-assembled at the state 

 capitol on Wednesdaj' morning. The discus- 

 sion of Messrs. Farquhar and Emery's papers 

 was first in order. The question was asked 

 whether the amount expended in the preserva- 

 tion of St. Anthony's Falls would not have 

 sufficed to establish and maintain an equivalent 

 plant of steam-engines. Dr. Emery thought 

 not. 



Prof. T. Eggleston followed with a paper on 

 ' An accident to steam-pipes arising from the 

 use of blast-furnace wool.' He attributed a 

 corrosion and subsequent explosion of steam- 

 pipes at Columbia college to the setting-free 

 of sulphur from the wool by the action of ex- 

 tremelj' diluted solutions of organic acids and 

 the rapid corrosion of the pipe by the sulphu- 

 ric acid, sustaining his position by reports of 

 anal3"ses and tests. 



He was strongl}- opposed hj Dr. Emery, 

 who claimed that the corrosion was due to 

 leakage and moisture, with alternate wetting 

 and drying of the pipes, and that blast-fur- 

 nace wool was entirely innocuous. 



Mr. John Lawler of Prairie du Chien de- 

 scribed the construction of the two pontoon 

 draws in the railwa3'-bridge across the Missis- 

 sippi at that place. Each pontoon is four 

 hundred and eight feet long, six feet deep, 

 thirty-six feet wide on bottom, and fort3--one 

 feet wide on top. The interior details, the 

 regulation of height of track, the means for 

 fastening and for manoeuvring the draws, were 

 described at length ; and the cost was stated 

 as one-sixth of the estimated cost of the usual 

 iron swing-bridge. The bridge was built in 

 1874, and has been in continued use ever 

 since. This bridge was seen from the train on 

 the trip from Chicago. 



The last paper at this session, by G. Lin- 

 denthal of Pittsburgh, Penn., was upon the 

 rebuilding of the Monons;ahela bridge at that 



place, from his design and under iiis direc- 

 tion. The first poi'tion of his i)aper entered 

 minutely into details of the new structure, and 

 was illustrated by tracings. The latter por- 

 tion was occupied with a discussion of tlie old 

 suspension-bridge, built in 1846 by John A. 

 Eoebling, the condition of the same before 

 removal, the tests of the material removed, 

 and the effect of the excessive overloading to 

 which it had been exposed for years b3' the 

 increasing and heav3' traffic over the bridge. 



After a brief discussion, the convention then 

 adjourned ; a portion of the members repairing 

 at once to Lake INIiunetonka, and the remain- 

 der going to Minneapolis, where visits were 

 made to the Washburn flouring-mill and to 

 the bridges. 



(To be continued.) 



KINETfC CnNSIDEtiATIONS AS TO 

 THE NATURE OF THE ATOMIC MO- 

 TIONS WHICH PROBABLY ORIGINATE 

 RADIATIONS.^ — I. 



The assumption that the mean kinetic 

 energ3- of translation of the molecules of a gas 

 is the measure of its temperature is one whose 

 beautiful agreement with experiment has led 

 to its acceptance as a necessarv part of the 

 kinetic theor3' of gases, and it has often led to 

 the thoughtless conclusion that this translator3' 

 motion is also the mechanical source of the 

 disturbances in the ether which oi'iginate radi- 

 ations. But there are man3- difficulties in the 

 way of accepting this view. One of the first, 

 and perhaps the least, is the difficulty of con-- 

 ceiving how such a motion of translation, which 

 is essentially longitudinal, can originate a lat- 

 eral vibration, such as light and radiant heat 

 must be. 



A greater difficulty appears to be found in 

 the extremeh' moderate mean velocit3- of trans- 

 lation which the molecules of a gas are found 

 to have. Molecular velocities, which are of 

 the same order of magnitude as that of sound 

 or of a rifle-ball, seem hardly fitted to cause the 

 necessar3' compressions or disturbances in a 

 medium in which the rate of proi)agation is so 

 immense ; or, to state it in another way, if 

 molecules, in describing their paths, originate 

 radiations, then the motion of a rifle-ball ought 

 also to do so, or, indeed, an3- much more mod- 

 erate motion, such as that of a vehicle or 

 animal. 



A still further difficulty is, that there is 

 another part of the kinetic theory which ap- 

 pears to be so related to this that both cannot 



1 Piesented in abstract to the Section of cliemistry anJ phys- 

 ics of the Ohio mechanics' institute, April 26, 18S3. 



