140 JOURNAL OF SCIENCE. 



Papers. — (1) " On a Deposit of Diatomaceous Earth at the Bay 

 of Islands," by A. McKay, F.G.S. The author stated that he had had 

 an opportunity of examining a deposit of diatomaceous earth about 

 half a mile to the east of the residence of the Hon. Henry Williams, 

 and that he brought samples from the upper surface, and from about 

 one foot below the surface of the deposit, which were submitted to 

 Mr. Maskell, who found only recent species in the samples from the 

 upper part, and fossil forms only in the samples taken at about a foot 

 from the surface of the deposit. Such being the result of the exami- 

 nations made by Mr. Maskell, on his describing the conditions under 

 which the deposit had accumulated, by way of explanation of the facts 

 Mr. Maskell suggested that probably an older diatomaceous deposit 

 had been denuded for supply of the lower part of the deposit under 

 description, and in which only fossil forms are found, while the higher 

 and last deposits were manifestly due to diatoms which (of recent 

 forms only) had lived and died within the area wherein their remains 

 had accumulated. But this is not the only explanation that may be 

 advanced, and he (Mr, McKay) deemed it necessary to describe more 

 closely the position of the deposit and the conditions under which it 

 had accumulated. After giving a full account of the locality in ques- 

 tion, and the position of the specimens collected, Mr. McKay stated 

 that on the stones and fern fronds which are under water when the 

 basin is full, the green living diatoms are deposited, forming a coating 

 of from ^in. to ^,-in. thick, according to circumstances. This deposit 

 round the margin of the basin soon bleaches white on the surface. 

 According to Mr. Maskell it is almost wholly composed of living 

 forms of diatomacefe. Very probably the same samples, Mr. McKay 

 thought, would be found among the grass-roots, and for the first few 

 inches into the deposit filling the basin itself. Unfortunately, Mr. 

 McKay did not bring samples to prove that such is the case ; but it 

 is so self-evident that this must be so that no doubts need be ventured 

 on the subject. The deposits in the middle of the basin are 6ft. to 

 8ft. thick, and were exposed by the cutting-down of a cattle-track 

 crossing the creek at this place. Mr. McKay took a sample from 

 about 1ft. below the surface. Some of this also was examined by Mr. 

 Maskell, whose decision as to the fossil nature of the species forming 

 this part of the deposit has already been stated. Subsequently Mr. 

 Maskell forwarded samples to England, which were examined bj r one 

 of the chief authorities on diatoms, whose decision was in accordance 

 with the conclusion Mr. Maskell had already arrived at. Such were 

 the facts of the case, and such the conclusions arrived at by competent 

 authorities. And yet he (Mr. McKay) was not satisfied that the true 

 explanation had been hit upon; and here he ventured a theory of 

 explanation to which, though there might be objections grave as 

 applied to Mr. Maskell's explanation, they were yet not the same, and 

 he had therefore written the paper so that the Society might have an 

 opportunity of debating the probabilities of each. Considering the 

 conditions under which the diatomaceous deposits had accumulated, 

 it was reasonable to expect that the recent forms of diatoms would be 

 found in the lowest, as well as the highest, beds of the deposit; and it 

 was certainly surprising that the upper beds, or latest part of the 

 deposit, should be wholly composed of recent species, which were 

 absent from the middle and lower parts. It was quite a possibility 



