Letter, from [J. E.] Benjamin Valz to Sir John Herschel, dated at Marseilles Autograph letter signed by sender. [Letter appears to be a response to some criticisms by John Frederick William Herschel of BV's paper on Encke's comet submitted to the Royal Astronomical Society] Deals with the density of the comet's nebulosity and with the effect of the comet's approach to perihelion, gives estimates of the comet's magnitude, and comments on the behavior of gases. 28 March 1839