54 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



explosions in most cases do not occur until several days after 

 the depression has reached its minimum. The greatest num- 

 ber of accidents are said to occur when a serious storm fol- 

 lows a long period of fair weather. Elevation of tempera- 

 ture, of course, greatly interferes with the natural ventilation 

 of a colliery ; and hence, if a warm day occur in a cold season 

 when natural ventilation is relied upon, it is very likely to 

 be followed by an explosion. For a like reason, the first hot 

 days of spring are quite often marked by colliery accidents. 

 16^4, July, 1872, 385. 



CYCLONES IN THE PACIFIC. 



Mr. Whitmer, in referring to a paper by Mr. Murphy in 

 Nature on the scarcity of cyclones in the Pacific, remarks 

 that there is rarely a year without at least one cyclone pass- 

 ing through, or in the neighborhood of, one of the Feejee, 

 Samoan, or Hervey group of islands. He states that the cy- 

 clone season extends over the greater part of the period dur- 

 ing which the sun is south of the equator ; consequently, 

 when the trade-winds from the north reach farthest south, 

 they are most prevalent about the middle, or a little later 

 than the middle, of the season, rarely earlier than December 

 or January. They are usually preceded for a few days by 

 strong northerly winds ; and if during such winds a sudden 

 fall of the barometer occur, this is considered a sure indica- 

 tion of an approaching cyclone. 12 A, June 13, 1872, 121. 



CHANGE OP TEMPERATURE IN THE NORTHERN HEMISPHERE. 



Mr. Howorth has been engaged for some time on a series 

 of papers discussing the changes that have taken place to 

 the present time in regard to the distribution of land and 

 water, and the consequent effect upon the climate. He finds 

 that the result has been a great increase in the amount of 

 cold in the far north, rendering regions such as those of East 

 Greenland, once capable of supporting a considerable popu- 

 lation, now entirely uninhabitable, and literally covered the 

 year round with snow and ice. He says, however, that while 

 the evidence is overpowering that the climate has been grow- 

 ing more severe in the highest latitudes, there is a great deal 

 of evidence to show the cold has decreased elsewhere, and 

 that, especially in view of the accounts given of the climate 



