BLUE GLASS A HOAX.

Clutha Leader, Volume III, Issue 156, 6 July 1877, Page 7

BLUE GLASS A HOAX.

(American AgrimUtnrist. Tn 1871, Gen. A. J. Pleasanton, of Philadelphia, published an account of his experiments with blue-glass, claiming that vines in a grapery partially glazed with glass of this colour, were vastly more vigorous in growth and productive of fruit, thau those under colourless glass. He also claimed that pigs, under violet glass, made a much more rapid growth than those in an ordinary pen, while a sickly bull-calf, placed in a bluo-glass pen, not only recovered at once, but in fifty days developed in a manner described by its owner as " marvellous." Those revelations do not appear to have created any general interest at the time, but last year (1876) a new edition of the work appeared, giving accounts of numerous alleged cures of disease in human patients, and other wonderful results on both plant and animal life, effected by blue light. Soon after this publication there was an excitement concerning blue glass ; and so many were disposed to make a trial of it, that the stock became rapidly taken up, while the price of tbe article was duly advanced. The newspapers helped the excitement by frequent articles, either taking a «erioufview of the matter, or turning it into ridicule. We received Gen, Pleasonton's work several months ago, though we can not say that we have read it/ as it is well nigh impossiblo for any one having a knowledge of the elementary laws of physics, to wade through it. The remarkable views presented as to light, electricity, magnetism, and matter in general, and the ease with which the most abstruse questions are disposed of by assertion, make the work a curiosity. The medical relations of blue light, we regarded as ono of thoso singular delusions that periodically possess the public mind in relation to curative menus, which would have its run, and if it did not lead to the neglect of proper treatment, might prove harmless. The influence of blue glass upon plant growth, being more in our line, we examined tho claims made for it, and finding those in such direct opposition to the facts established by men of •icience, we did not think it worth while to present the matter to our readers. Recently, however, letters of inquiry have come, and as we learned that several persons were taking out the plain lights from their green -house.-., and replacing them by blue ones, we found 4 necessary to say something on the subject, As we were about to write on blue glass, there came most opportunely to hand an article from Peter Henderson, Esq., which being, as his articles usually are, the result of experience, will carry "more weight with our readers than a presentation of the matter in any other form.

WHAT PETER HENDERSON KNOWS ABOUT THT. ...liUfECT 01>* BLUE .-HOI-XT Oj* VLANXS.

Five years ago, (though utterly sceptical as to its value,) f, at the urgent solicitation of a friend, used a blue transparent wash on the glass of one of my greenhouses, thus changing the glass practically into blue • on the glass of another house, of similar dze, I used whitewash. Both greenhouses were filled with plants of a similar character. In a few weeks wo found that the plants in the house under the bluo glass were " drawing," or spindling up, more than under the white, and on examination of a thermometer, placed in each house, it was found that, during the two first weeks in June, the average temperature, under tlie blue glass, was 00 deg., while under the white it was 80 deg. This was just such a result as might have been expected, the darkened glass absorbed the sun's rays, and the heated glass gave off its heat to the interior of the house, while the whitened glass -reflected them, that was all. The temperature was simply increased under the blue glass, and to the great detriment of the plants, for all cultivators know that in our hot summer months, the difficulty we havo to contend against is too high a temperature. If Gen. Pleasanton started to -force his grapery in midwinter, his blue glass would be apparently beneficial — not because it was blue, but because it would assist him in getting a higher temperature, which would-, at that season, be desirable ; or, for the same reason, his pigs might feel somewhat more, comfortable, and fatten more quickly. But were he to carry on the culture of either under the blue glass into midsummer, both pigs and grapes would be likely to remonstrate. Upwards of 30 years ago, it was claimed that seeds would germinate, and cuttings root, quicker, under dark-coloured than under lightcoloured glass ; this is no doubt true, and irom the same cause—an increased temperature under the dark glass, but all who have had experience in such matters, well know that this " forcing " process is at the health of the subjects so treated, unless indeed they are piants indigenous to tropical countries, to which a high temperature is natural. To claim that blue glass, or any other coloured glass has any proper ties capable

of affecting health, in other manner than what is due to an increased temperature, produced by any other means, is undoubtedly false.

Mr Henderson no doubt assigns the proper reasons for whatever seemingly favourable influence blue glass may have upon the plants growing beneath it. Tliat there is any peculiar powar in tho blue ray to accelerate plant growth, which our readers aro well aware depends primarily upon the decomposition of carbonic acid, liberating the oxygen and the assimilation of the carbon, is disproved by the results, obtained by various careful experimenter;-.. Indeed, the rays of the blue end of tho spectrum are much less favourable to the decomposition of carbonic acid by plants, than yellow rays, and either alone greatly inferior to all the rays together — or white light. . The experiments of Pfeffer (Sachs's Lehrbuch der Bolanih, 1875), show that the amount of decomposition under white light being 100, tho red-orange rays had a decomposing power equal to 82.1 ; the yellow, 40.1 ; green, 15.0, while tho blue and violet rays are only 7.6. We were quito amused with the strong common sense view of a friend, who, in speaking of the subject, remarked : — " If blue light were best for plant growth, the Creator would have provided it in tho beginning." Should any of our readers desire to give their plants blue light instead of white, we would warn them that its application is patented ! Blue rays are an essential part of white light, and some court may yet decide that tho use of the greater involves the less, and we were all infringing upon the patent. At last accounts white light is not yet covered by a patent, but one can not tell what may happen.