43

of the Solar Syjiem.

into the shadow C; in passing throughit, stie becomes wholly darkened at L, andleaves the shadow at O. This is called atotal eclipse: and when the moon’s centerpasses through that of the shadow, whichcan only happen at the very time she is inthe node at N, it is called a central eclipse.

We have not yet mentioned the atmo-sphere, which requires our consideration,while we are treating of lunar eclipses; forthe shadow of the earth does not reach themoon. In fig. 21. T represents the earth,BCD Bgf its atmosphere, AB, AB,rays proceeding from the fun at 8, touchingthe atmosphere at B and B; these gostraight on, and terminate the shadow of theatmosphere at H. The moon is constantlyenlightened by the fun’s rays until she en-ters this shadow, when sire becomes fainter,as she continues to move between A B Hand ABU.

The rays which enter the atmosphereobliquely, are refracted, and bent intocurves that touch the earth; all the lightbetween F f and G g, is intercepted by the

earth;