Penrhyn Quarries Slate Calculator
Penrhyn Quarries Slate Calculator
First series
Second series
Third Series
Other slate information
National archive slate records
Penrhyn slating calculator
Links
Front
Back
This calculator was produced by Penrhyn Quarries (McAlpine Slate Ltd) in 1986, just before desk top computers became commonplace. It is one stage in the development of roof design tools from books to spreadsheets.
Penrhyn slate calculator large view 1986
Hower’s Lightening roof calculator 1888
(pdf download from Quarries and beyond website)