James Timmins Chance to Faraday   17 November 1860

Glass Works near Birmingham | 17 Nov. 1860.

To | Professor Faraday | &c &c

Report of the alterations made in the Dioptric Apparatus at the South Lighthouse at Whitby.

1 - Height of the lamp in relation to the Refractors. The lenticular panels have not a common focal plane; and as I had no authority to readjust the lenses, the lamp has been so placed that 28mm is the maximum distance of the burner below the sea horizon focus of any refracting panel.

The 2d, 3d, 4th, and 5th panels, counting from the North have their respective sea horizon foci from 27mm to 28mm above the burner, whereas the 1st panel has its sea horizon focus only 25mm above the burner.

I doubt not that this last panel is better placed for sending the brightest light to the sea horizon, than the other three (though not intentionally.) The due position of the burner, both vertically & horizontally, is defined by the intersection of two wires or strings to be passed & stretched, diametrically through two pairs of holes fixed permanently for that purpose on the uprights of the apparatus.

2 - Upper Reflectors.

The sea-horizon focal line of each prism has been made to pass through a point 28mm above the burner & 30mm behind the axis of the system.

3. Lower Reflectors

The sea-horizon focal line of each prism has been made to pass through a point 25mm above the burner, & 40 mm before the axis.

4 Lamps

The South Lighthouse is at present provided by me, temporarily with two good mechanical 4-wick lamps and the requisite supply of surplus burners &c &c. I purpose, however, sending ultimately two pressure 4-wick lamps; as I prefer the greater simplicity of construction of this kind of lamp.

Signed James T. Chance.

Memorandum.

The metallic reflectors, at the South Whitby light, are not being used at present, in consequence of the injury which the reflected heat of the flame now so much increased causes to the burner. This is a matter for future investigation.

J.T.C.