From these experiments, we may conclude, that water-lizards, and most probably the other amphibious animals, die in nitrous oxide in a much shorter time than in hydrogene or pure water; consequently their death in it cannot depend on the simple privation of atmospheric air. At the season of the year in which this investigation was carried on, I was unable to procure frogs or toads. This I regret very much. Supposing that cold-blooded animals die in nitrous oxide from positive changes effected in their blood by the gas, it would be extremely interesting to notice the apparent alterations taking place in their organs of respiration and circulation during its action, which could easily be done, the membranous substance of their lungs being transparent. The increase or diminution of the irritability of their muscular fibre, might be determined by comparative galvanic experiments. VIII. _Effects of solution of nitrous oxide in water on Fishes._ _a._ A small flounder was introduced into a vessel filled with solution of nitrous oxide in water over mercury. He remained at rest for ten minutes and then began to move about the jar in different directions. In a half an hour he was apparently dying, lying on his side in the water. He was now taken out, and introduced into a vessel filled with water saturated with common air, he very soon recovered. _b._ Of two large thornbacks,[188] equally brisk and lively. One, A, was introduced into a jar containing nearly 3 cubic inches of water, saturated with nitrous oxide, and which previous to its impregnation had been long boiled; the other, B, was introduced into an equal quantity of water which had been deprived of air by distillation through mercury. [188] I use the popular name. This fish is very common in every part of England; it is nearly of the same size and color as the minnow, and is distinguished from it by two small bony excresences at the origin of the belly. It is extremely susceptible. A, appeared very quiet for two or three minutes, and then began to move up and down in the jar, as if agitated. In eight minutes his motions became very irregular, and he darted obliquely from one side of the jar to the other. In twelve minutes, he became still, and moved his gills very slowly. In fifteen minutes he appeared dead. After sixteen minutes he was taken out, but shewed no signs of life. B was very quiet for four minutes and half. He then began to move about the jar. In seven minutes he had fallen on his back, but still continued to move his gills. In eleven minutes he was motionless; taken out after thirteen minutes, he did not recover.