From Adam Walker
London Augst. 20th. 1787
I have seen Your Harpsichord safe Packed and hope it will arrive safe to you.
The Instrument remaining so long in my hands, has given me time to observe where the chief defects of the Celestina stop lay, and also of the machine that moved it. I am sorry to say that altho it answerd in some degree better than the common Fly Wheel, yet I found by use and time it was very liable to be out of order, and particularly as it had to go by Sea. In short I cou’d not safely trust it, to give you satisfaction on the arrival. I therefore judged it best to take it off, and apply a Fly Wheel (on an improved Plan) in its stead. The Motion of this is so exceedingly easy, it can be no objection to the performer and giving it a few quick impulses at will the Wheel will continue to move two or three Minutes. If, at any future period I succeed in the construction of a Machine for the above purpose, I shall most certainly send one of them to you, without any additional Expence.
Directions for the Celestina
When this Stop is used, 1st. draw the outside Knob (on the right hand of the Instrument) quite out, and move the middle Knob (which is the 2d. Unison) towards the right. 2d. Press down the Left Pedal, or let the Stay, which is connected with it, hold down the Pedal, and so disengage the Foot, then the Left foot applied to the Center Pedal, or Traddle will put the Wheel in Motion. The first action of the foot on the Traddle gives the Wheel an impulse in the right direction, and in which it shoud be continued. N.B. The Loudest Effect of the Celestina is producd, by increasing the Speed of the Wheel, with the pressure of the Keys. The Right Pedal for the Swell Lid has a good affect with the Celestina, observing that the pressure of the Fingers and the Pedal correspond. When the above position of the Stops has been formed, the Celestina affect is on the Upper Keys, and a soft additional Stop, as an accompaniment to it, is on the Lower. This will be found a great improvement of the Celestina, adding great variety to its affects, for by this divice may Two performers accompany each other, the Rapid Lesson on the Lower, and the Viola or Sostenuto accompaniment, on the Upper. Or a performer may accompany a soft Cantabile Air, with an Harpeggio or running Bass on the Lower Keys, and may change positions by playing fine holding Notes like the Violoncello with the left hand on the Upper keys, and a Rapid movement with the right, on the Lower Keys. When the Full Harpsichord is required, Let the Stops and Pedal be in their first Position, viz, the Celestina Knob Slid inwards, the Center Knob on the right, moved towards the Left hand, this puts the 2d. Unison on. The Pedal being Up, the full Tone of the Instrument is produced.
A Quantity of Silken Bands, Knotted to a proper measure and ready Rosin’d, are sent, with a Vial of the Liquid Rosin, which is prepared by mixing about ⅓ in Bulk of Powder’d Black Rosin to the best Rectified Spirit of Wine. A New Band may be put on once pr. Month or oftener, if much used, and Rosin’d in 4 or 5 days, or when the Sound appears lower than usual. The manner of Rosining, is by holding the piece of Cloth dip’d in the Liquid to the Band, whilst it circulates once or twice over it, and then leave it ten Minutes to dry.
RC (DLC); unsigned; endorsed by TJ: “Walker.” Recorded in SJL as received 20 Nov. 1787.