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THE POPULAR SCIENCE MONTHLY. 



cream is to aid its " ripening." Dairymen 

 let their cream ripen before churning, be- 

 cause their experience shows that from such 

 cream butter " comes " more readily, keeps 

 better, and is of better flavor than from 

 sweet cream. In a recent paper on this 

 subject, Dr. H. W. Conn states that milk 

 will become contaminated with bacteria if 

 put into vessels in which particles of curd 

 and grease are left sticking in joints and 

 on the sides. Boiling in water will kill 

 the bacteria, but their spores or seeds can 

 not be killed without a higher heat. Hence, 

 to prevent the souring of milk, cans and 

 pans should be set on a stove or in the 

 oven a few minutes after washing. As cold 

 checks the development of bacteria, the milk 

 should be cooled immediately after it is 

 drawn from the cow, and kept as cool as 

 possible. Cream for butter, on the contrary, 

 should be kept in a warm place, so as to 

 favor the growth of bacteria. Dairymen 

 sometimes add a little old cream to a fresh 

 lot as a leaven. Acid is also added for the 

 same purpose, but this is of doubtful use. 



A Fire-ball in Art. In the Madonna 

 painted by Raphael for Sigismondo dei Con- 

 ti dal Foligno, the Virgin is represented as in 

 the clouds, the clouds rest upon a rainbow, 

 and under the bow is a red fire-ball. As- 

 suming that the introduction of so unique a 

 feature as a fire-ball in a painting of the 

 Madonna is symbolic, Prof. H. A. Newton 

 has inquired into the history of the subject. 

 He finds that on the 4th of September, 1511, 

 there fell near Crema, some leagues south- 

 east of Milan, a number of stones, the re- 

 sults of the explosion of a meteorite, which 

 are described by several authors ; and he 

 believes that Raphael intended to represent 

 this aerolite in his painting. He seeks to 

 interpret its meaning by finding what men 

 thought of such phenomena. When the En- 

 sisheim stone fell, nineteen years earlier 

 than this one, near the lines separating the 

 contending French and German forces, the 

 Emperor Maximilian had the stone brought 

 up to the castle, and held a council of state 

 to consider what the fall meant. Sebastian 

 Brant, in a poem describing the fall, speaks 

 of the terror it caused to the Burgundians 

 and French. Eleven years later, in 1503, 

 Maximilian, in a proclamation appealing for 



aid, included the Ensisheim stone-fall among 

 indications of divine favor. After the fall 

 of 1511, although the papal forces were de- 

 feated in battle, the French were forced to 

 withdraw in June, 1512, from Milan and 

 northern Italy. It is natural, then, to sup- 

 pose that Raphael in the picture united in 

 his painting the fire-ball with the rainbow 

 in order to symbolize divine reconciliation 

 and assistance. 



The Highest Mexican Volcano. One of 



the results of the recent scientific expedi- 

 tion of Prof. Angelo Heilprin and his com- 

 panions to Mexico was the establishment of 

 Orizaba as the highest of the giant volca- 

 noes of that country. The barometrical 

 measurements of the four highest volcanoes 

 gave for Orizaba, 18,205 feet; Popocate- 

 petl, 17,523 feet; Iztaccihuatl, 16,960 feet; 

 and Nevado de Toluca, 14,954 feet. In fa- 

 vor of the accuracy of the measurements, 

 Prof. Heilprin refers to the quality of his 

 registered . aneroid barometer, which was 

 tested and corrected at Philadelphia before 

 and after starting, at Vera Cruz, and in the 

 city of Mexico ; and the fact that all the sum- 

 mits were ascended within three weeks, and 

 were measured with the same instrument, 

 during a period of atmospheric equability 

 and stability which is offered to an unusual 

 degree by a tropical dry season. The meas- 

 urements bring up the question of what is 

 the culminating point of the North Ameri- 

 can continent. The only other mountain 

 than Orizaba that need be considered in this 

 connection is Mount St. Elias, in Alaska. 

 The measurements of this mountain, how- 

 ever, depart so widely from one another 

 that we are not yet in a position to affirm, 

 even within limits of a thousand feet or 

 more, how nearly it approaches in height 

 the Mexican volcanoes. The most usual 

 figure in standard publications is 14,970 

 feet ; Malespina found, by taking the angles 

 from Port Mulgrave, 17,851 feet ; Teben- 

 koff reduced this figure by somewhat more 

 than 900 feet. Mr. Dall, in 1874, made 

 angular measurements from four points, 

 69, 127, 132, and 167 miles away, that gave 

 results varying from 18,033 to 19,596 feet. 

 He does not place great confidence in any 

 of them. In view of the broad divergence 

 existing in the later measurements, and the 



