The death of General Augustus James Pleasonton at Philadelphia last Thursday will recall vividly to many persons the famous "blue glass craze" that swept the length and breadth of this country about nineteen years ago. The craze also affected Europe, and was for several years discussed among scientific men.

General Pleasonton had been a soldier, but left the Army to practice law. He devoted a great deal of his time to scientific research and experiment, and in the course of his investigations got the idea that the blue of the sky must have some important effect upon living organisms of this earth. Tests of the alleged peculiar properties of blue light had been made some years before in Europe but with unsatisfactory results. General Pleasonton made experiments with blue light at his farm at Overbrook, just outside Philadelphia. In the autumn of 1860 he erected a cold grapery, 84 feet long, 26 feet wide, and 16 feet high at the ridge. The structure was finished in March of the following year. Then he busied himself in deciding the quantity of blue glass he needed. Too much would produce too great action, he thought, and militate as much against the success of the test as if too little were used. After computing the surface of the building, General Pleasonton concluded to insert blue glass panes in every eighth row, the other rows being of ordinary glass. He alternated the rows on opposite sides of the roof so that in the daily course of the sun there would be a colored shaft of light on every leaf and  p118 twig in the building. The sides and ends of the grapery were fitted with separated runs of violet glass.

Soon after the building was completed twenty varieties of grape cuttings one year old were planted, and they grew amazingly. Four weeks after planting the inside of the roof and walls were covered with a healthy and luxuriant growth of vine and foliage. There were no blemishes on any of the leaves or shoots, and the insects generally found on grape vines were absent. General Pleasonton spoke to his friends of the promise given by his vines under the novel treatment, and early in September, 1861, the grapery was visited by Mr. Robert Buist Sr., a prominent agriculturalist and grape grower. Mr. Buist was lost in admiration and amazement. He told the General that he had cultivated grape vines for forty years and had visited the finest vineries of Scotland and England, but never in his life had he beheld anything like the vines before him. He added that some other vines planted at the same time as those of General Pleasonton had attained a length of only five feet, while the vines matured under the colored glass were forty-five feet long and an inch in diameter one foot above the soil.

The greatest of care was given to the vines, and in March, 1862, they began to bear. The number and promised size of the grape bunches were considered wonderful, and the individual grapes were enormous. The following September Mr. Buist returned to visit General Pleasonton, bringing with him a very successful grape grower who had heard of the marvelous progress of the vines. After a careful calculation the General was informed that his vines were laden with no less than 1,200 pounds of grapes. This was astounding to the visitors, as in countries where vines have been grown for many hundreds of years new vines require five or six years before they put forth a single cluster of grapes, whereas the blue glass grapery was produ­cing in seventeen months. The vines bore again in the season of 1863, and the yield, calculated by a comparison with the previous yield, was two tons of large grapes.

The news of such wonderful forcing spread to every agriculturist  p119 in the country. Many persons discredited the statements. Nevertheless, the blue glass craze had begun, and blue glass graperies were constructed in many States with success. General Pleasonton received scores of letters of inquiry and congratulations and statements of marvellous results.

His success with the grapes tempted General Pleasonton to consider experiments with animal life. To this end he built a piggery on his farm, with the roof and three sides constructed of blue glass and plain glass in equal proportions. He then selected eight Chester county pigs of a promising litter and put four in the blue glass pen and four in an ordinary pen, where they would be subjected to the natural rays of the sun. The pigs were two months old. Those in the blue-glass pen weighed 167½ pounds and those in the other pen 203 pounds. Each pig in the experimental enclosure was lighter than the lightest pig in the other. The pigs were cared for in the same manner and fed on the same measure of the same food by one man. They were kept in the pens from November 3, 1869, until March 4, 1870, and were then weighed. It was found that three of the blue-glass pigs had gained 398 pounds, whereas three in the natural pen had increased only 386 pounds. To offset this difference was the fact that the fourth sunshine pig had gained twenty-seven pounds on the fourth blue-glass pig. The General explained this by saying that the latter was not in such good condition at the start as his rival. At any rate, the experiment was deemed highly successful, and further advanced the blue-glass theory.

General Pleasonton's next test was made on an Alderney bull calf, born January 26th, 1870, and so puny and feeble that it was not expected to live many days. The animal was placed in the blue-glass pen, and in twenty-four hours his feebleness began to diminish, and in a few days he was decidedly vivacious. Five days after birth the calf had grown noticeably. In fifty days he was six inches taller and had developed laterally in proportion.

The calf experiment caused as much of a sensation as the grape and pig experiments, and skeptics began to waver. Blue glass was in great demand, and agriculturists and experimenters  p120 of all kinds built blue-glass houses and grew all sorts of things in them. Very soon General Pleasonton had a large and enthusiastic following. The daily papers published many accounts of what were claimed to be cures and improvements in health resulting from the use of sunlight filtered through panes of violet or blue glass. A woman who had been ill for a long time with some constitutional weakness was not only strengthened but absolutely cured in a short time by sitting in blue light and a man whose arm was crippled by rheumatism declared that he experienced almost immediate relief when the arm was thrust within the violet rays. A child that was not expected to live gained eighteen and a half pounds in four months, or an average of four and five-eighths pounds a month, from the blue-glass treatment. General Pleasonton purchased a mule that had been in the army and had been rendered deaf by the discharge of artillery and rheumatic by exposure, and began experimenting with the animal. Panes of blue glass were arranged to cast rays on the mule's neck, head, and shoulders all day. In a short time the mule recovered his hearing, and was relieved of the rheumatism. The removal of the deafness was explained by General Pleasonton as having been effected by electro-magnetic currents induced by the lights over the auditory nerves.

General Pleasonton received so much encouragement that on September 26th, 1871, he applied for and received a patent on an "Improvement in Accelerating the Growth of Plants and Animals." The blue-glass idea was then taken up by silkworm growers in Italy, who found that, whereas 50 per cent of the worms died ordinarily, of those reared under blue-glass screens only 10 per cent perished. In May, 1871, General Pleasonton delivered, before the Philadelphia Society for the Promotion of Agriculture, a lecture on "The influence of the blue ray of the sunlight and of the blue color of the sky in developing animal and vegetable life, in arresting disease and in restoring health in acute and chronic disorders to human and domestic animals." The lecture was the result of experiments made from 1861 to 1871.

The basis of General Pleasonton's theory was the difference  p121 in the action of the various rays of the spectrum. In his lecture he said the sky was remarkably blue at the equator and in the Arctic regions, and the exuberance of vegetable growth in the region of the former and the rapid growth of vegetable life in the latter were said to be unequalled in any other portions of the globe. From this the lecturer said it would be easy to imagine the enormous influence exerted by the blue of the sky, combined with the sun's white light and heat and the moisture of the regions. As an example of this influence, General Pleasonton brought forth the subject of the green color of the leave of plants. Blue combined with yellow makes green, being darker when blue predominates and the reverse when yellow is in excess. When a seed is planted a white threadlike root emerges from its lower end. From the top of the seed protrudes a white swelling, which changes color as its approaches the surface of the soil. The swelling is the embryo leaf, which absorbs yellow from the earth, which latter is brown, being a combination of yellow and black. As the leaf gets into the influence of the blue sky it absorbs the blue light, which mixes with the yellow and forms green, light at first, but darker as the blue is exerted. Then, after the plant blossoms and goes to seed, the blue in the leaves is eliminated and they become yellow, and, after absorbing the carbon of the plant, become brown and die. This shows, said the General, that the blue ray is the symbol of vitality and the yellow of decay and death.

Another phase of General Pleasonton's theory was that blue light excites magnetism and electricity, by which carbonic acid gas evaporated from growing plants is decomposed and the oxygen thereof liberated, to be absorbed again in maturing the plant and stimulating the active energies into fullest development. He also held that if the blue light of the sky is not electro-magnetic in itself it induces electro-magnetism, and, applying it at the early spring time, when the sky is bluest, stimulates after winter's torpor to supply carbon and oxygen to plants and enhance their growth.

The lectures of General Pleasonton were collected and published in 1876 with some of the letters he had received. The  p122 book was printed in blue ink on tinted paper, as an experiment in avoiding the glare gaslight induces in ordinary ink and paper.​a

Editorial
Blue Light in Therapeutics

Some years ago, General Pleasanton,º of this city, created quite a stir in circles that should have judged more critically, by his experiments upon the effect of keeping animals and vegetables under blue glass. He asserted that blue light has a most marvellous effect upon all forms of life, and his views were received with a good deal of favor. They even found practical advocates in our profession, so that blue glass and blue paper made their way into hospital wards, and very great therapeutic value was even attached to them by some physicians. Recently our attention has been called to the subject by an elaborate and laudatory paper on the medical use of blue light, in one of the homoeopathic journals.

It is a very curious circumstance that all the writers and experimenters believe that there is an active virtue in blue light, and that a person under blue glass gets more of this blue virtue than does a person upon whom nature's sun shines unobstructed. A moment's consideration ought, however, to teach the veriest tyro in science that the blue glass does not add anything to the sun's ray, but only takes away from it. The light beneath the blue glass is blue not because the glass had altered or colored it, but because the glass had obstructed the passage of the other rays of the spectrum, and has allowed the blue to pass alone. A man in the hospital ward gets the same amount of blue light on him whether colored glass be there or not. To attribute active therapeutic powers to the colored light is therefore, scientifically speaking, foolishness.

We have also failed as yet to discover any good grounds for believing that light as made by the Creator contains anything deleterious to life, or that it can be improved artificially. The gentleman previously alluded to did seemingly show that the pigs raised under blue glass were finer than those of the same litter who had shared the common lot of their brethren, and did certainly raise very large crops of grapes in greenhouses into the roof of which blue glass had been placed. As we are under obligations to him for great courtesy, we are sorry that scientific candor forces us to state, after careful examination of his experimental procedures, that in them he violated the primary canons of scientific experimentation, and that his results are really of no value.

We saw the two sties, with their pigs. The "blue sty" was large and clean, airy and dry, with a few blue panes here and there in its roof; the other sty was exposed, dirty, and wet. The pigs in the "blue sty" got practically as much daylight as idd the others, only the magic blue light once in a while crossed their pathways. The result, to our mind, simply showed that pigs, like their ilk even among mortals, are amenable to the beneficence of hygiene.

It is hardly worth while to say a word about the grapes, since there were no comparative results. magnificently-situated grapery, under-drained in the most expensive and scientific manner, with a deep, rich compost bed, in which vines of the most approved character were planted and tended by a skilful gardener, of course yielded large crops of grapes.

It was four or five years ago that we made the inspection, but, if our memory be correct, the blue lights constituted only one-third or less of the roof, so that the grape-vines were not deprived of other light.

Of course, we are open to conviction upon any scientific subject, but, if there be any truth at all in the doctrine of evolution, life must have adapted itself in the course of the last ––––– millions of years to light as it is, and experiments to disprove this, in order to be convincing, must be conducted by those who appreciate the difficulties and necessities of scientific experimentation: certainly the burden of proof lies very heavily upon any one who attempts to improve sunlight.