Very interesting account of an 18th Century trip.

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On Boxing Day of 1799 the twenty-year-old chemist Humphry Davy stripped to the waist, placed a thermometer under his armpit and stepped into a sealed box specially designed for the inhalation of gases, into which he requested his assistant, Dr. Kinglake, to release twenty quarts of nitrous oxide every five minutes for as long as he could retain consciousness.

The experiment was taking place in the lamp-lit laboratory of the Pneumatic Institution, an ambitious and controversial medical project where the young Davy had been taken on as laboratory assistant. In the centre of the laboratory, he had set up a chemical reaction: nitrate of ammoniac bubbled in a heated retort, and the escaping gas was being collected in a hydraulic bellows before seeping through water into a reservoir tank from which the sealed box was filled. After an hour and a quarter, by which time he estimated that his system was fully saturated, Davy stepped out of the box and proceeded to inhale a further twenty quarts of the gas from a series of oiled green silk bags.

While seated in the box breathing deeply, Davy had felt the effects that had become familiar from his many previous experiments since he had first inhaled the gas earlier that year. The first signature was its curiously benign sweet taste, followed by a gentle pressure in the head as he continued to inhale. Within thirty seconds the sensation of soft, probing pressure had extended to his chest, and the tips of his fingers and toes. This was accompanied by a vibrant burst of pleasure, and a gradual change in the world around him. Objects became brighter and clearer, and the space in the cramped box seemed to expand and take on unfamiliar dimensions.

Now, under the influence of the largest dose of nitrous oxide anyone had ever taken, these effects were intensified to levels he could not have imagined. His hearing became fantastically acute, allowing him to distinguish every sound in the room and seemingly from far beyond: a vast and distant hum, perhaps the vibration of the universe itself. In his field of vision, the objects around him were teasing themselves apart into shining packets of light and energy. He was rising effortlessly into new worlds whose existence he had never suspected.

Somehow, the whole experience was irresistibly funny: he had ‘a great disposition to laugh’, as all his senses competed to exercise their new-found freedom to its limit.

Now the gas took Davy to a dimension he had not previously visited. Objects became dazzling in their intensity, sounds were amplified into a cacophony that echoed through infinite space, the thrillings in his limbs seemed to effervesce and overflow; and then, suddenly, he ‘lost all connection with external things’, and entered a self-enveloping realm of the senses. Words, images and ideas jumbled together ‘in such a manner, as to produce perceptions totally novel’: he was no longer in the laboratory, but ‘in a world of newly connected and modified ideas’, where he could theorise without limits and make new discoveries at will.

After an eternity he was brought back to earth by Dr. Kinglake removing the breathing-tube from his mouth; the outside world seeped back into his ‘semi-delirious trance’ and, as the energy returned to his limbs, he began to pace around the room. Yet a part of him was still present in the dimension of mind that had swallowed him whole, and he struggled for the words to capture it. He ‘stalked majestically’ towards Kinglake ‘with the most intense and prophetic manner’, and attempted to shape the insight that had possessed him. ‘Nothing exists but thoughts!’, he blurted. ‘The world is composed of impressions, ideas, pleasures and pains!’