72 TWENTIETH ANNUAL REPORT ON THE STATE CABINET. 



Winter. Summer. Difference. 



T f ^n ^ Penzance __ 44.6 60.4 15.8 



i^at. OU ^Banioul__. _ 6.6 61.9 55.3 



-^ on ^Madeira __ 61.3 70. 8.7 



l^at.dU ^Cairo 55.5 84.6 29.1 



And for examples on our own continent and one inland from 

 each coast : 

 i From the Pacific : 



r Fort Humboldt... 45.2 57.4 12.2 



Lat.40 <! Salt Lake -. _ _ 32.1 75.9 43.8 



I^FortMadison ...26.1 78.1 52.0 



From the Atlantic : 



Bermudas 59.2 75.2 16.0 



Lat.30 ^;^T^tclies 49.8 79.9 30.1 



From these comparisons, it appears not only that the contrast 

 between summer and winter increases as we go inland, but also 

 that it is greater in the high latitudes than nearer the equator. 



This fact is important to the vegetable productions. Many of 

 our most valuable crops — being annuals — care nothing for the cold 

 of the winter, if they can but have the requisite heat in the sum- 

 mer ; and others, which are indeed perennial, as grapes, peaches, 

 &c., can be protected against frost in the inland winter, so as to 

 produce most abundant and delicious fruits in the summer ; which, 

 however, will not arrive at maturity at all at the sea coast on the 

 same isothermal line, for want of the greater heat of summer wdiich 

 they find in their inland position. England, for example, does 

 not produce grapes, with an average for the year of 50 deg., two 

 at least more than our own, and winters no more than 40 ao-ainst 

 our 25.5 ; while in the neighborhood of Astracan and coastwise, 

 with the same general average for the year as England, and 

 winters averaging at least eight or ten degrees colder than ours, 

 and twenty-five degrees colder than those of England, " grapes 

 and fruits of every kind are as beautiful and as luscious as in the 

 Canaries," although the vines must be buried several feet deep in 

 the winter to preserve them from frost. 



The temperature of places that have no great inland distance is 

 modified by the sea currents that may happen to flow near their 

 coast. The eftects of these currents are scarcely felt in latitudes 

 near the tropics. The Gulf Stream, for example, which flows 

 from the Gulf of Mexico, deflects the isothermal line of 32 deg. 

 for the year, from latitude 55 wdiere it leaves the American conti- 

 nent, to 75 north in the North Atlantic near the Island of Spitz- 



