98 SCIENCE. [1899.
calcareous and silicious layers, meet their explanation. If the lower stratum of the sea is getting warmer, a deposit of shells and other remnants of cretaceous organisms is inevitable, and the formation of a silicious deposit must be difficult if not impossible ; whereas, when the lower stratum is cooling, calcareous particles are dissolved and silicious matter is thrown down.
Herr Kahlenberg has confirmed a statement that solutions of sodium and potassium silicates are hydrolytieally decomposed into the corre- sponding hydroxide and colloidal silicic acid ; and he concludes that in natural waters silicic acid always exists in the colloidal state. And it may be further noted that Mr. Clarke has made observations on the degree to which natural silicates are attacked by pure water, which is rendered alkaline in proportion to the amount of destruction it accomplishes. Thus mica, muscovite and lepidolite are but slightly affected, phlogopite, a magnesian mica, more so, and oligoclase and albite are more affected than orthoclase. This corresponds with the susceptibility to weathering of these minerals.
The action of organisms has long been recognised as a geological factor, as in the building up of tufa and travertin by phormidium. It now appears that the presence in peat of vanadium, chromium and titanium in North Carolina, as recorded by M. Baskerville, and the occurrence of chalybite and vivianite in the peat of Holland, as related by Herr van Bemmelen, must be attributed to organic processes.
On the other hand, paleeotrochis, the regularly striated biconical objects that were thought to be silicious corals occurring in rocks regarded as sedimentary in North Carolina, are now proved by Mr. Dillet to be concretionary substances enclosed in volcanic rhyolites.
Meteorology.
Rain fell at Greenwich on 142 days in the year. The least number in any month was five in August, and the greatest was twenty-one in April. The total fall was 22-20 inches, which was 2-18 inches less than the mean of fifty-five years.
In August, the dryest month, the deficiency was 211 inches, and in November, the wettest month, there was an excess of 1*46 inches. The winter was mild and the summer was hot.
On February 10 the maximum shade temperature was 67° Fahr., or 6° higher than any maximum for that month for sixty years. During the first fortnight of February the country was swept by a succession of gales; but after the 15th no rain was recorded over a large part of England, and on the 27th there was an absence of rain throughout the whole of Western Europe, which had been covered by an anticyclone since the 19th. Nevertheless, rain fell at Greenwich on twelve days, and the total precipitation for the month was 0-45 inch in excess of the mean.
At Upernivik, in Greenland, the mean temperature of twenty-one years was 16-2° Fahr., with an absolute maximum of 64°, and an absolute minimum of - 411°. The average rainfall was 8-9 inches.
It has been ascertained, from observations made in our own country, that in nearly all cases the annual temperature of the soil at the depth
