Baltimore
Feb 20 1880

Dear Sir,

The following is a brief summary of the work of my parties since leaving Evensburgh.

The work at York has chiefly had reference to the vexed questions in regard to the flexure of the pendulum stand. An interesting series of experiments both statical & dynamical have been made there under various conditions & upon different stands. Several points have been brought out in this way; particularly that a weight upon the stand has no such influence as Plantamour maintains. I find a weight of 25 lbs absolutely without influence. Hence, Plantamour's experiments

Experiments have also been made upon the rollers made to replace knife-edges. These have been disappointing, as the friction appears much increased.

At present, the length of the pendulum is getting measured. When this is done, we shall return to the flexure investigation, experimenting to ascertain by direct experiment whether the change of the period of oscillation corresponds to the statical or to the dynamical flexure.

The spectrum metre work approaches completion. Many new comparisons have been made at New York, chiefly at low temperatures. These continue to agree beautifully and the relative coefficients of expansion are found to be nearly what had been supposed from the slight variations of temperature at which former measures had been made.