VEGETABLE PHYSIOLOGY AND ELECTRICITY. 



163 



VEGETABLE PHYSIOLOGY AUD ELECTRICITY. 

 Petzholdt's Agricultural Cliemistiy, is of 

 itself sufficient to justify public coufidence in 

 the ' Farmers" Librarj-,' as a work which is to 

 elevate the character of the fanner by iuduciug 

 the application of scientific principles, and a 

 method of investigation to his routine of daily 

 duties. The only \\-ay to elevate (not in Mike 

 Fink's plirase, when he told his brother, who 

 was shooting tlie tin cup off" his head, ' to elevate 

 his gun a little lotrcr,') the fanner is to tlirow 

 into his way such infonuation as M^ill first teach 

 him that tliere are eiTors in his present system, and 

 that, not only these en'ors are to be corrected, but 

 that new methods of farming and new applica- 

 tions of old substances, and the discoverj- of new 

 ones, either as pabulum for plants or modifica- 

 tions of the texture of the soil can only be the 

 result of scientific stiidy and experiment. Petz- 

 holdt has been well selected for this object. 

 The greatest objection to the work is the want of 

 a proper Glossarj-, which I prophe.sy will also 

 be the case with most future publications of this 

 kind. Even ik/s reader felt the necessity of a 

 fuller one, although some years since, Chemistry 

 had formed a part of his sj-stem of^tudies. I 

 propose, at some early period, to supply that 

 deficiency, if not done more satisfactorily by 

 some one having moi-e leisure and preparation. 

 In the mean time I beg leave to make an extract 

 from the ' Botanic Garden ' of Dr. Darwin, the 

 Poet and the Phi/siolosist of Nature. The 

 'Botanic Garden' was published m 1781, and tlie 

 lines selected embrace two subjects, which are 

 thought worthy of discussion : the one by Petz- 

 holdt in Lectm-e VIII, on the Carbon of Plants, 

 and the other at page 109 of your Monthly 

 Journal, entitled 'Electricity applied to Agri- 

 culture and Horticulture.' Dai-win was a man 

 of genius, and his own age did not comprehend 

 him. His prophesy on steam has been substan- 

 tially realized, and his ' Loves of the Plants," is 

 tlie school-boy's philosophy of the Botanist. But 

 to the extract and the notes which arc taken 

 from Part I, Canto 1. lines 4.57 to 472. callin" 

 " from their long repo.se the Vernal Hours." 

 '■ On wings of flame, ethereal virgins ! sweep 

 O'er Earth's fair bosom and complacent deep ; 

 "V\Tiere dwell my vegetative puwer.s benumb'd, 

 In buds imprison'd, or in bulbs intomb'd. 

 Pervade pellucid Forms .' their cold retreat, 

 Ray from bright urns your viewless floods'of heat; 

 From Earth's Jeep wastes electric ton-ents pour. 

 Or f bed from Heaven the scintillating shower ; ' 

 Pierce the dull root, relax its fibre trains, 

 Thaw the thick blood, which lingers in its veins ; 

 Welt whh w.-mn breath the ft-agriuit giima that bind 

 The expanding foUage in its i^caly rind ; 

 And as in air the laughing leaflets play,' 

 And turn their shining blossoms to the ray, 

 Njinplie ! with sweet cmile, each openin" flower 



invite, 

 And on ite damask eyelids pour the light." 



Line 462. The fluid matter of heat, or calo- 

 rique, in which all bodies are immersed, is as 



(319) 



necessary to vegetable as to animal existence. 

 It is not yet determinable whether heat and 

 light be different materials, or modifications of 

 the same materials, as they have properties in 

 common. They appear to be, both of them, 

 necessary to vegetable health, since, without 

 light, green vegetables first become yellow ; that 

 is, they lose the blue color, which contributed to 

 produce the green; and afterwards they also 

 lose the j'ellow and become white ; as is seen 

 in cellerj' blanched or etiolated for tlie table by 

 excluding the light from it. 



The upper surface of leaves, which I suppose 

 to be their organ of respiration, seems to require 

 light as well as air ; siuce plants which grow in 

 windows, on the inside of houses, are equally 

 solicitous to turn the upper side of their leaves to 

 the light. Vegetables, at the same time, exude or 

 perspu-e a great quantity from their leaves, as 

 animals do from their lungs; this perspirable 

 matter, as it rises from their fine vessels, (per- 

 haps much finer than the pores of animal skm,) 

 is divided into inconceivable tenuity, and when 

 acted upon by the Sun's light, appears to be 

 decomposed ; the hydrogen becomes a part of 

 die vegetable, composing oils or resins ; and the 

 oxj'gen combined with light or calorique, as- 

 cends, producing the pure part of the atmo- 

 sphere, or vital air. Hence, during tlie light of 

 daj-, vegetables give np more pure air than 

 their respiration injures (see Petzholdt,) but not 

 so in the night, even though equally exposed to 

 warmth. This single fact would seem to show- 

 that light is essentially different from heat ; and 

 it is perhaps by its combination with bodies, 

 that their combined or latent heat is set at lib- 

 erty. [Your readers can pursue this and similar 

 points in additional note XXXIV, and in the 

 notes generally.] 



Line 463. Electric torrents pour. The in- 

 fliience of Electricity in forwarding the gerrai- 

 nofion of plants and their groictk seems to be 

 pretty well established, though Mr. Ingenhouz 

 did not succeed in his experiments, and thence 

 iloubts the success of otliers ; and though M. 

 Rouland, from his new experiments, believes 

 that neither positive nor negative electricity in- 

 creases vegetation, botli which philosophers had 

 previously been supporters of the contrary- doc- 

 trine;, for many other naturalists have since 

 repeated tlieir experiments relative to this object, 

 and tlieir new results have confinned their for- 

 mer ones. Mr. D'Ormay, and the two Roziers. 

 have found the same success in numerous experi- 

 ments which they have made in the last two 

 years ; and Mr. Carmoy has shown, in a con- 

 vincing manner, that electricity acceleotes ger- 

 mination. 



"Mr. D'Ormay not only found various seeds 

 to vegetate sooner and to grow taller, which 

 were put upon his insulated table and supplied 

 with electiicity, but also, that silkwonns began 



