Vol. XXII. No. 1.] 



POPULAR SCIENCE NEWS. 



11 



when the light at the side is lowered, and that 

 at the back raised again, the second transform- 

 ation takes place : and thus the exhibition can 

 be continued indefiniteh'. 



In order that the plaster bust may be re- 

 moved from the stage for inspection, the glass 

 must be arranged so that the assistant behind 

 the scenes ma}' slide it away toward C at the 

 right moment. As the glass is not set in any 

 frame, the movement will not be noticeable, 

 especially if the front part of the stage is 

 rather dimly lighted. Care must be taken to 

 have all parts of the stage completely covered 

 with black cloth or paper, so that the back- 

 grounds on which the images appear shall have 

 the same appearance in each case. Plate- 

 glass is much the best for this experiment ; 

 but, as it is rather costly, and not always to be 

 obtained, a good quality of ordinary "Ger- 

 man " window-glass ma}" serve a good pur- 

 pose. The size is unimportant, as the stage 

 opening maj' be made to fit anj- available piece 

 of glass ; and smaller objects may be used for 

 the dissolving views if the glass is too small 

 to admit of the reflection of a living head. 

 The minor details and precautions will suggest 

 themselves to anj" one who attempts to pro- 

 duce this entertaining optical illusion, which 

 we especially recommend to the attention of 

 onr younger readers. 



A MAMMOTH SNOW-FLAKE. 

 The engraving represents in its natural size 

 a single snow-flake which fell at Chepstow in 

 Wales on the 7th of January last. It meas- 



ured 3.6 inches in length, 2.4 in breadth, and 

 1.3 in thickness, and when melted gave about 

 one-half a cubic inch of water. It was com- 

 posed of numerous separate crystals which had 

 adhered together while falling through the air. 

 The atmospheric conditions were very favor- 

 able for the formation of large flakes, as the 

 temperature was just above the freezing-point, 

 which rendered the snow moist and coherent, 



and the air was perfectly calm and saturated 

 with moisture. 



During this storm the snow fell in remark- 

 able quantity. About one-fifth of an inch 

 fell in six minutes, which when melted was 

 equivalent to about one twenty-fifth of an inch 

 of water. 



This is certainly one of the largest snow- 

 flakes on record ; and if any of our readers 

 observe anj- of equal or larger size during the 

 present winter, we should like to be informed 

 of their dimensions. 



♦ 



[Specially reported for the Popular Science ^etcs.] 



METEOROLOGY FOR NOVEMBER, 1887, WITO 

 REVIEW OF THE AUTUMN. 



TEMPERATURE. 



ATXBAeB Thkbmoiibteb. 



AtTA.M 33.00' 



Atip.M 46.57" 



At"? P.M 35.60* 



Wbo\e month j 38..W 



BecoDd average . . . . ! 37.64' 



Last Beventeen Nor's . 

 Second average . . .^ 



Autumn of 1887 . . . . 

 Last seventeen autumns, 



38.06* 

 37.68* 



48.13* 

 60.15* 



Lowest. 



17* 

 21* 

 10* 

 10* 

 10* 



Highest. I Range. 



56' 

 66' 

 54' 

 66* 

 86* 



i 31.12*, 42.51*,) 

 i In 1873. in 1877. 



42.36* 



10* 



47.53*, 

 in 1875. 



39' 

 45° 

 44' 

 66* 

 56' 



11 .41* 

 11.74* 



63.57", I 

 in 1881. i 



68* 



6.04* 



The last day of the month was emphatically the 

 coldest, by more than ten degrees, having an aver- 

 age of only 16°; the closing observation (10°) was 

 the lowest point. The warmest day was in near 

 proximity, the 27th, with an average of 52§°; in- 

 dicating a very sudden change. In three days fol- 

 lowing, the mercury went down 44°. The highest 

 point reached was 66°, on the 4th and 7th. From 

 the 26th to the 28th was unusually warm for the 

 season, suddenly followed by cold, as unusual. The 

 entire month was three-tenths of a degree above 

 the average of the last seventeen Novembers, while 

 the autumn was nearly two degrees below that 

 average (see the table). The extreme autumns 

 have been 47.53°, in 1875, and 53.57°, in 1881,— 

 a range of over 6°. Only two autumns have been 

 colder than the present in seventeen years. 



The face of the sky in 90 observations gave 52 

 fair, 17 cloudy, 13 overcast, 7 rainy, and 1 snowy, 

 — a percentage of 57.8 fair. The average fair for 

 the last seventeen Novembers has been 55 5, with 

 extremes of 40 per cent, in 1885, and 74.4, in 1874. 

 Four mornings were foggy, of which three were 

 consecutive, on the 25th to 27th, and very dense, 

 especially that on the 26th, which continued through 

 most of the day and evening. The average fair 

 during the autumn was 55 8 per cent, while that 

 of the last seventeen autumns has been 57.9 per 

 cent, with extremes of 43.9, in 1882, and 69.2, in 

 1874. 



PRECIPITATION. 



The amount of rainfall the past month was 2.42 

 inches, while the average for the last nineteen 

 Novembers has been'3.92, with extremes of 1.10, in 

 1882, and 7.45, in 1877. The rain fell principally 

 on six days; the largest amounts were .90 inch, on 

 the 1.5th, and .76, on the 10th. A trace of snow, 

 the first in the. season, fell on the 11th. The 

 amount of precipitation since Jan. 1 has been 

 40.21 inches, while the average for this period has 

 been 41.80. The amount of precipitation through 

 the autumn has been 5.76 inches, while the aver- 

 age for the last nineteen autumns has been 10.41, 



with extremes of 3.42, in 1874, and 20.08, in 1869 

 (including a flood). The next highest amount 

 was only 14.10, in 1872. The amount the present 

 autumn has been the lowest, with one exception, in 

 nineteen years. 



PRESSURE. 



The average barometer the last month was 29.976 

 inches, with extremes of 29.29, on the 11th, and 

 30.68, on the 30th. This is a remarkably high fig- 

 ure; and though just equalled in March last, it has 

 been exceeded but twice in fifteen years. The first 

 two-thirds of the month the pressure was very 

 changeable, with no very low depressions; while 

 the last third was more steady, ending the month 

 very high, and still rising. The average pressure 

 for the last fourteen Novembers has been 29.977 

 inches, with extremes of 29.840, in 1878, and 

 30.193, in 1880. The sum of the daily variations 

 the past month was 7.14 inches, giving an average 

 daily movement of .238 inch. This average in 

 fourteen Novembers has been .231, with extremes 

 of .127 and .293. The largest daily movements 

 were .69, .67, and .63, all in connection with rain- 

 fall. The average pressure for the last autumn 

 was 30.021 inches, that of the last fourteen autumns 

 30.001 inches, with extremes of 29.881, in 1875, 

 and 30.070, in 1880. 



The direction of the wind in 90 observations gave 

 16 N., 1 S., 3 E., 24 W.,6 N.E., 20 N.W., 1 S.E., 

 and 19 S.W., — an excess of 21 northerly and 53 

 westerly over the southerly and easterly, and indi- 

 cating the average direction of the month to have 

 been W. 21° 37' N. The westerly winds in the last 

 eighteen Novembers have uniformly prevailed over 

 the easterly, with an average of 48.89 observations, 

 and the northerly over the southerly, with four ex- 

 ceptions, by an average of 14.22; indicating the 

 approximate general average for November to be 

 W. 16° 13' N. The longitudinal extremes in 

 eighteen Novembers have been 7 and 73 W., — a 

 range of 66 observations; and the latitudinal 44 N. 

 and 12 S., — a range of 56. The relative progres- 

 sive distance travelled by the wind the last month 

 was 57.01 units, and during the last eighteen 

 Novembers 880 such units, — an average of 50.92; 

 showing less opposing wind the past month than 

 usual. The winds were 5° 24', or near half a point 

 more northerly than the average, and yet the month 

 was a trifle warmer than usual. The average direc- 

 tion of the wind the last autumn was W. 25° 29' N., 

 while the average for the last eighteen autumns 

 has been only W. 11° 30' N. ; showing the influence 

 of the more northerly winds, and also greater cloudi- 

 ness, in producing the cool autumn. 



D. W. 



Natick, Dec. 6, 1887. 



——* — 



[Specially reported for the Popular Science Kewit from the 

 Observatory of the College of New Jersey.] 



ASTRONOMICAL PHENOMENA FOE 

 JANUARY, 1888. 



Mercury cannot be seen during the month. It 

 passes superior conjunction with the Sun on Jan. 

 18. Venus is still a morning star, rising about 

 three hours before the Sun. This interval will be 

 somewhat diminished by the close of the month. 

 Mars is gradually growing brighter, and rises ear- 

 lier than before. It is in quadrature with the Sun 

 on the morning of Jan. 5; that is, it is on the 

 meridian about 6 a.m. It rises at about midnight 

 on Jan. 1, and at about 11 p m. on Jan. 31. It is 

 near the first-magnitude star Spica {Alpha Vir- 

 ginis), and during the month moves from a point 

 about 7° west, to a point about 4° east, of the star. 

 Jupiter rises at about 4 a.m. at the beginning of the 

 month, and at about 2.30 a.m. at the end. On 



