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Pyrheliometer, pir-hē-li-om′e-tėr, n. an instrument for measuring the intensity of the sun.—adj.

Humphreys gathers together and amplifies all that he and Abbot and Fowle have previously said as to observations of the sun's thermal radiation by means of the pyrheliometer.

Herschell’s actinometer and Pouillet’s pyrheliometer, instruments for ascertaining the absolute heating effect of the sun’s rays, should, however, be more generally employed by meteorologists.

A few days previous to the beginning of that year, Herschel began observing at the Cape of Good Hope with an "actinometer," and obtained results agreeing quite satisfactorily with those derived by Pouillet from experiments made in France some months later with a "pyrheliometer."

This Volume deals with the letters "P," "R," "S," and any person wishing to master a few really interesting subjects for dinner conversation will read and learn up all about Procyon, Pizemysi, and Pyrheliometer, Quotelet, Quintal, and Quito, Regulus, Ramazan, Rheumatism, Rhynchops, Rum-Shrub, and Rupar, Samoyedes, Semiquaver, Sahjehanpur, Silket, Sinter, and Size.