C z )

is lost by every reflection, and that every reflection dothduplicate, triplicate, quadruplicate, quintuplicate, &e.the first preportionof loss. For Instance:

Suppose I have a Helioscope made of an Object Glass,an Eye Glass, and four Reflecting Glasses, and that, by the firstreflection, I lose | of the Direct light, I affirm there will re-main but ^ part of the Direct rays of the Sun, which can fallupon the eye at the last, for if every reflection doth lose■! of its Rays, and reflect but 5, and that quarter loseth|, andreflects only ^ of its received Light, there will remain buta part of the whole, and if this sixteenth part loseth threequarters of its Rays, and reflects only a fourth, it will follow,the remainder will only be £ part of the whole, and if that beonce more reflected, the Ray will return but with £5 part of itsfirst light.

This, although it be obvious, andeafie enough now it isknown,yet I do not find that any Person hath yet had thoughtsof applying it to this use. The generality of Observers havehitherto made use of, either some very opacous and thickGlasses next the Eye, whether of red, green, blew, or purpleGlass; others have diminished the Radiation, by coveringtheGlafles with a very thick and close coat of the foot of aLamp; others, by casting the figure upon a piece of whitePaper, whence ’tis reflected to the eye ; Others have contra-cted the Aperture into a less circle, and thereby let in lessLight* and so make use of one single Ray instead of a pencilof Rayes; Others have expanded the figure of the Sun, bythe help of Eye Glasses, into a circle of ten, twenty, or anhundred times its Diameter. But none of all these waiesdo comenear this which I now describe by the help of three,four,or more Reflections,as any one upon trial will very plain-ly diseoveir.

Firsts As to the co'oured Glasses, I cannot at all approveof them, because they tinge the Raves into the same colour,and consequently takeoff the tru:hof the appearance, as toColour; besides, it superinduces a haziness and dimnessupon the Figure, so that it doth not appear fliarp and di-stinct. The same inconvenience is also produced by MonsieurHugenius's way, of covering the Glass with the scot of a

B 2 Lamp,