In this manner we can form a conception of the growth of the wonderful structure which has brought forth the majority of the stellar bodies that we discern. The spiral nebulæ visible at the Galactic poles are similar formations but probably of far more modest dimensions. They may compare to the Milky Way as the smaller planets to the Sun. According to recent investigations the spiral nebulæ seem also to possess an enormous velocity and they have probably invaded the Milky Way from without. As previously stated, an exceedingly remarkable conception of the Milky Way exists among the Mexicans. To them it is the Matrix of all and gave birth to the stars, the most important of which are the Sun, the Moon, and Venus. This idea evidently agrees very well with the results of investigations in the last few years. Finally, a few words about the extent of the Milky Way. So far we have not been able to measure it; only rather uncertain approximations are possible. Wolf estimates the diameter, that is the distance between the two spirals at the point where the Sun now is, to be about 10,000 times the distance from the Sun to the nearest fixed star, Alpha in Centaurus, which distance on the other hand is about 10,000 times the distance from the Sun to the remotest known planet, Neptune, or 300,000 times that from Sun to Earth. Expressed in the usual units, we arrive at 40,000 light years or 400,000 trillion kilometres (240,000 trillion miles). Lord Kelvin makes another estimate of 6000 light years, that is seven times smaller. The mean diameter of the nebula proper might be about five times larger, in round figures one hundred thousand light years, or one billion billion kilometres (600 million billion miles). Like a monstrous octopus, the Milky Way swims in the fathomless ether-sea. Its dimensions are about as many times larger than those of the earth as that globe is larger than an atom. This has caused the gifted Irish physicist Fournier D’Albe to consider the celestial globes as atoms, out of which systems of the order of the Milky Way are constructed in the same manner as the earth and other stellar bodies are upbuilt with atoms, invisible to us and yet measured with an incredible degree of accuracy.