ASTRONOMY AND METEOROLOGY. 351 



more than others ? and he found a remarkable difference in the 

 winter months ; the greatest in January, whose mean temijerature 

 in the twenty-nine years ending 1799 was 34° 7' ; the mean of the 

 next thirty years was 35° T, and of the last thirty years was 37° o', 

 and every season showed increase. The author then selected 

 every day of remarkably low and remarkably high temperature, 

 and divided the results into groups, and it appeared that in the 

 twenty-live years ending 1838 tliere had been seventy-two days 

 in January whose mean temperature had been below 25°, and 

 fourteen only of such low temperatures in the last twenty-live 

 years, whilst in the former period there had been seventy-live 

 days of temperature higher than 45°, and 109 days of temperature 

 exceeding 45° in the latter. He treated every naonth in the same 

 way, and discussed the early observations and descriptions of 

 years in the last century, and concluded, — that our climate in tlie 

 last hundred years has altered ; that the mean temperature of the 

 year is now 2° higher than it was one hundred years ago ; that 

 the month of January is nearly 3° warmer ; that frosts and snow- 

 showers are of very much shorter duration and less in amount ; 

 and he concluded his paper by expressing a hope that series of 

 observations in progress over the world will be patiently continued ; 

 — for other questions now open themselves, for instance, has any 

 part of the world lost 2° of annual temperature ? or has the world 

 itself increased in warmth ? Other questions also press, so as to 

 make it extremely desirable that similar determinations should be 

 made as soon as possible at other parts of the world. 



CLIMATE OF BRAZIL. 



According to Professor Agassiz, in his lecture before the Lowell 

 Institute, in Boston, Mass., in October, 1866, the climate of the 

 Amazonian basin differs from that of other regions in the same 

 latitude, by reason of the great moisture prevailing there. The 

 comljination of heat and moisture, he observed, j^roduces a more 

 luxuriant vegetation than is to be found anywhere else. 



There are not four distinct seasons, as with us ; but perpetual 

 summer reigns. There is more or less of rain throughout the 

 year, but no such special period of great prevalence as marks the 

 climate of other tropical regions, wliere a very dry season suc- 

 ceeds months of copious rain. The rains do not prevail over all 

 sections at the same time, but beginning at the south in Sc^ptem- 

 ber, they progress northward till they reach Guiana in JMarch and 

 April. As a consequence, when the southern tributai-ies of t!ie 

 Amazon are most swollen, the northern tributaries are at tlieir 

 lowest ebb, and vice versa ; and thus a balance is maintained 

 between the ujoper and lower parts of the basin. 



Again, there is a difference between the course of the main 

 stream at its most western origin, and at its mouth. The swelling 

 waters of the Madeira reach the Amazon in November or Decem- 

 ber. The northern tributaries pour in their waters at a later 

 period. The great increase in the Amazon at its confluences, by 

 temporary coincidences in the flow of its tributaries, is in or near 



