Letter, from Giovanni Antonio Plana to Sir John Herschel, dated at Turin Autograph letter signed by sender. Is helping another scientist bring to publication a work on triangulation in the Alps. Comments on John Frederick William Herschel's idea of suspending an extremely long plumb bob at a particular precipice in the Alps [Foucault pendulum?]. Giovanni Plana does not believe the results would warrant the expense. Comments on the floating collimator [see John Frederick William Herschel's 1825-1-14], noting that he does not find it very helpful. 24 March 1825