Light visible and invisible : a series of lectures delivered at the Royal Institution of Great Britain, at Christmas, 1896 (1897)
Thompson, Silvanus Phillips, 1851-1916, Royal Institution of Great Britain · New York : Macmillan · leaf 36
he graduatedbench between the lights whosebrightness is to be compared to-gether, and set in such a way thatone light shines on one paraffinslab, and the other light on theother slab, as in Fig. 9. If theilluminations on the two sidesbalance the edges of the slabs will seem equally bright.But if… … Fig. 9. 1 This paraffin slab photometer is the invention of Dr. Joly,V. R.S., of Dublin. It is an exceedingly satisfactory instrument. Light No.11 Light No.2 7\ / w \
Light · X-rays
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