Proceedings and Report of the 1st-15th Annual Meeting

Proceedings and Report of the 1st-15th Annual Meeting

By American association of farmers' institute workers

An interesting bit of reading.

Heliothermometer (updated December 25 2023)

An insulated box with a thermometer inside, sunlight is allowed in through a window with three panes of clear glass, to measure sunlight, but not the outside air.    

Horace Bénédict de Saussure (1740-1799), a Swiss natural scientist, used Mariotte’s insight to design and build a “heliothermometer” to measure the relative intensity of sunlight. It was an insulated box with one side consisting of three layers of glass separated by air layers. 

source
source

Image and conflicting information about altitude here

Not found on Wikipedia (Aug 7 2015)

Found in an IPCC report (archived)

Dec 25 2023, still not found on Wikipedia