210 



THE POMOLOGIST AND GARDENER. 



1871 



mountains. The variation of temperature at differ- 

 ent altitudes is attributed to the fact that the lumin- 

 ous rays of heat from the sun pass through a clear 

 atmosphere, with but little loss from absorption ; 

 they, therefore exercise but little heating effect upon 

 the air. When these rays strike the earth, they are 

 absorbed, and the surfsicc, be it land or water 

 becomes heated, and gives out rays of obscure heat. 

 The latter pass easily through absolutely dry air, 

 but are arrested, as Professor Tyndall has shown, 

 by the aqueous vapor which is almost invariably 

 present in the lower strata of the atmosphere. Thus 

 the air near the surface becomes warmer than the 

 super-incumbent strata; but instead of mixing with 

 the colder air above performs a mechanical office 

 giving out its heat, and actually becomes colder as it 

 ascends — so that fiom 80 degs. Fahr. it is cooled to 

 33 degs. by the time it reaches a higlit of 15,000 

 feet. Humboldt from many observations on this 

 subject, has developed highly interesting facts con- 

 nected with this subject. The allowance of 1 deg. 

 Fahr. for every 100 yards of ascent, is a rule suffi- 

 ciently close, and easily recollected. 



Large masses of land or proximity to the ocean, 

 exercise considerable influence on the climate ; 

 great masses of water moderates by its action on 

 the winds, the heat of summer and the cold of win- 

 ter. Prof Tyndall has a lengthy article on the 

 properties of aqueous vapor. He says : " The 

 aqueous vapor is a blanket more necessary to the 

 vegetable life than clothing to a man. It prevents 

 the iron grip of frost, it warms the fields, like a 

 local dam, by it the temperature at the earths' sur- 

 face is deepened ; it finally overQows and gives to 

 space all it receives from the sun— that is, the sun 

 raises the vapors of the equatorial ocean ; they rise, 

 but for a time a vapor screen spreads above and 

 around them." I will briefly sum up the leading 

 facts— about " aqueous vapor" — atom for atom the 

 absorption is 16,000 times that of air. The power 

 to absorb and the power to radiate are perfectly 

 reciprocal and proportional ; hence it will radiate 

 with 16,000 times the energy of an atom of air. 

 Into space it pours its heat, chills itself, condenses, 

 and the tropical torrents are the consequence. 

 The air expands and is refrigerated. The rain 

 quits the ocean as vapor and returns as water- 

 without naming other climatal phenomena. 



Thus the absence of this vapor in the central posi- 

 tion of Iowa renders the winter more severe. It 

 must be remembered that a clear day and a dry day, 

 are very different things. The atmosphere may 

 possess great visual clearness, while it is charged 

 with aqueous vapor, and on such occasions great 

 chilling cannot occur by terrestrial radiation. We 

 will now compare California with Iowa, and exam- 

 ine the face of the country of Upper California— 

 the coast mountains, the high peaks and inland 



mountains. The low land or central or Sacramento 

 basin lying east of the coast range, for 350 miles 

 long and 50 wide. Fogs prevail from May to Sep- 

 tember, and keep the summer cool, decreasing as 

 we recede from the ocean ; south of 35 degs. the 

 fogs are rare and the summer heat greater. The 

 average fall of rain at Fort Yuma is annually but 

 4 inches, San Diego 10, San Francisco 32, and Hnm- 

 boldt Bay 34 inches. Sierra Nevada, at an altitude 

 of 5,000 feet, 44 inches, varying with the height and 

 latitude along the coaet. South of Sacramento 40 

 degs., rains are rare between May and November, 

 which is the dry season. The variation of the mean 

 temperature is most rapid about the Middle latitude 

 of 45 degs. in consequence of the transitions are 

 more rapid ; it is these sudden changes that baffle 

 the fruit-grower — and where the gravelly soil pre- 

 vails the radiation is more rapid — and what might 

 prove a plenteous season of rain in one section 

 would occasion drouth in another, so that the 

 inches of water that fell in one place, is no criteri- 

 on, unless it is shown that other things are equal. 



The mountains affect the climate of the adjacent 

 plains in various ways — by the reverberation of 

 heat from naked rocks ; by affording shelter from 

 certain predominating winds; and by giving rise to 

 descending currents of cold air from the higher 

 regions of the atmosphere, in consequence of the 

 disturbance of the eqilibrium of heat produced 

 by the radiation from their sides and sum- 

 mits, so that while the sun's rays fall upon 

 it at a less oblique angle, it is sheltered from 

 the cold winds blowing from a higher latitude. 

 All this is favorable to California, and the re- 

 verse to Iowa, which demands a diflerent theory 

 to account for the fertility it possesses, and the suc- 

 cess in fruit culture. Hence, also it is true that 

 grain of all kinds matures and comes to the great- 

 est perfection with a much less amount of rain in 

 California than is necessary to serure a much less 

 perfect crop in Iowa or the adjoining States. Con- 

 sider the statements made preceding and the con- 

 clusion is easily arrived at or the solution of the 

 question propounded. 



As regards the latitude between the two States 

 taken centrally, would not make more than 5 degs. 

 further north for Iowa — yet, it is far removed from 

 both the Atlantic and Pacific Oceans, and the 

 aqueous vapors arising therefrom. Compare the 

 extremes of heat and cold during the year in Iowa, 

 with the same variation in California, where it 

 hardly differs 10 degs. during the whole year, on an 

 average, for the locality of San Francisco. How is 

 it at Des Moines? Iowa is, with few exceptions a 

 rolling prairie, and a soil that needs saturation dur- 

 ing May and June, to supply the requisite moisture. 

 I have not posted myself as to the various condi- 

 ions of the soils in various localities, and simply 



