in the Temperature of JFhtter. 39 



with the results of Dr. Holyoke's seven years observa- 

 tions at Salem, which make the mean temperature of 

 the three winter months 25° 76. With this desrree of 

 cold, fresh water rivers are annually covered, and held 

 bound with solid ice. 



To cover v/ith ice salt streams, bays and arms of the 

 sea, a greater degree of cold is requisite, and this degree 

 occurs many times every century. 



If then a mean temperature of 25 or 26 degrees by 

 Farenheit will keep the American rivers covered with 

 ice for many weeks, we have further evidence that the 

 Rhine and Danube, fresh water rivers, must be frequent- 

 ly froze in modern times. Dr. Williams states the mean 

 degree of cold at several places in Europe, as follows : 



At Vienna, in 1779 and 1780, January, 27° 5 



February, 33 23 



At Ratisbon, in 1781 and 2, January, 30 52 



February, 30 76 



At Manheim, in 1781 and 2, January, 35 08 



February, Q>^ 08 



From these means he deduces the general mean of 

 31° 8 for January, and ZZ"^ 6, for February, which, he 

 says, will accurately express the temperature of a Ger- 

 man winter on those rivers. Admit this conclusion, and 

 what follows ? The undeniable consequence that a Ger- 

 man winter is almost as cold as a New- England winter; 

 for the mean temperature of January in Vienna was 27° 

 5 — the mean temperature of an American winter is 25° 

 76. The difference is only one degree and twenty-nine 

 hundredtJis. The difference between the general mean, 

 of January above stated, 31° 8, and the general mean of 

 America, of 25° 76, is only 5° 32. If the vibrations of 

 heat and cold are as great on the Rhine and Danube as 

 in America, which is understood to be the fact, those 

 rivers must be froze every winter, although perhaps not 

 sufficiently in a common winter, to sustain loaded car- 

 riages. Certain it is that the cold at Manheim and Ra- 

 tisbon is nearly equal to any thing experienced in New- 

 England. In the Memoirs of the American Academy, 

 part 1 of vol. 2, page 88, Dr. Holyoke has stated the 



