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Page:Popular Science Monthly Volume 57.djvu/318

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308
POPULAR SCIENCE MONTHLY.

containing the lens loaned by Professor Young pointing directly skyward.

That it will be impracticable to give here all of the disc of the moon in the large photographs, will be evident when it is considered that the lunar circumference on each plate is about 4 feet; but it will be inferred from the examples that the prominences and polar streamers as well as their features, appear in imposing magnitude and detail.

Many of what it is hoped will be the most interesting photographs still await development, but Mr. Smillie's thorough preparation is promising adequate results.

Heat of the Corona.

Mr. Abbot, with aid of Mr. Mendenhall, appears to have measured

PSM V57 D318 North polar coronal streamers.png
Fig. 3. North Polar Coronal Streamers. Taken with 15 inch Lens of 135 feet Focus. Exposure 16 Seconds.

the heat of the corona, and in spite of previous efforts, this is probably the first time that it has been really shown to exist. For five minutes before second contact, the bolometer was successfully exposed to the region of the sky close to the narrowing crescent of the sun where the corona was shortly to appear. A diaphragm was interposed in the beam having an aperture of only 0.4 sq. cm. Deflections, rapidly diminishing from 80 to 6 mm. were obtained, the last being about 40 seconds before totality. Then the diaphragm was opened to 290 sq. cm. and a negative deflection of 13 mm. was observed after totality, where these positive deflections had just been found, showing that the corona was actually cooler than the background which had been used at the room temperature. Next the black surface of the