ELISHA MITCHELL SCIENTIFIC SOCIETY. 105 



3. KeIvIvER. Studien iiber die Organisation und Entwicklung der Chal- 



iueen. Zeit. f. w. Z. 1880. 



4. Schmidt, Oscar. Zur Orientining iiber die Entwickluug der 



Schwiimme. Zeit. f. w Z. 1875. 



5. Fiedler. Ueber Ei und Samenbildung bei Spongilla fluviatilis. 



Zeit. f. cu. Z. 1888. 



6. Dezso. Die Histologic und Sprossenent\vicklung der Tethyen. 



Archiv Mikr. Atiat., Bd. 16 and 17. 1879 and 1S80. 



THE TRANSITION CURVE. 



BY WM. CAIN, C. E. 



The ideal transition curve for railroads, to pass from a 

 tangent to a circular curve of given degree, is one whose 

 degree of curvature is zero at the point where it leaves the 

 tangent (P. C.) and increases directly as its length, meas- 

 ured along the curve from the P. C, to where it connects 

 with the circular curve, at which point it should have the 

 same tangent and rate of curvature as the circular curve. 

 By the use of such curves on railroads, street-car lines, etc., 

 to ease off the ends of circular curves, the super-elevation 

 of the outer rail is gradually attained without shock; and 

 the sudden change from the tangent to the circular curve 

 so often experienced on unadjusted circular curves, with 

 its annoying and damaging lurch, is avoided. 



Mr. A. M. Wellington (see Engmeering News for Janu- 

 ary 25th and February 8th, 1890) was the first to propose 

 this particular curve, which he regarded as practically 

 identical with the cubic parabola. Recently, Mr. Conway 

 R. Howard has published in his Transition Curve Book an 

 analysis of the subject founded on known principles of the 

 cubic parabola, which this curve closely approximates to 

 for flat arcs. 10 



