THE LENGTH OF OUR VOYAGE
frost settles on it; and in this state meteors have often been found by those who have seen them flash down, have marked the spot where they fell, and hastened towards them as quickly as possible. Mr. Gregory has kindly cut some of his meteors so that you can see where this thin outer crust stops; you see how very little had time to get heated; all the inside remained cool.
Here is a specimen which should be of particular interest to the ladies present, because it has diamonds in it: not very large ones, but still unmistakable diamonds. Mr. Parsons (whom you all know, I hope, as the inventor of the turbine) tells me that he thinks these diamonds are made when two meteors strike one another. I have told you at what fearful speeds they travel, 50 or 100 miles a second, say; and if two of them hit, the pressure developed must be enormous, far greater than anything we can imitate on this Earth. And Mr. Parsons further tells me that he believes all diamonds are made in this way. He has himself tried many times to make diamonds without success, and he thinks it is because he cannot get pressures nearly big enough; and so he inclines to the view that all the diamonds we find have been brought to the Earth by meteors which fell on it in ages past. This makes us look with increased respect at Mr. Gregory's collection, doesn't it?
But diamonds are not the only substance meteors have brought us; shut up inside them various gases have been found. Where were these gases collected? Probably in the upper layers of our own atmosphere. You remember how we regretted that the sounding-balloons were not able to bring us down samples of