Letter, from Luke Howard to Sir John Herschel, dated at Ackworth Autograph letter signed by sender. Has been applying his mode of calculation for the barometrical heights for the years 1815-23 and sent the results to the Royal Society [of London] As John Frederick William Herschel may not see them he sends a few comments on them. Would like a suitable colleague to share his labors. 22 February 1840