§ 1. A short description of some temperature observations in the Madüsee has been published in the Scottish Geographical Magazine for December 1910, and this communication aims at giving a more complete description of the observations with a first attempt at the mathematical discussion of oscillations at the surface of separation of two liquids in a basin of varying depth and cross-section.

The majority of the fossils described in this paper were collected by the late Dr Marcus Gunn on the coast of Sutherland between Brora and Helmsdale, more especially on the beach of Culgower Bay in the neighbourhood of Culgower (Maps I. and II.). It is several years since I first had an opportunity of seeing Dr Gunn's collection at his house in London: at that time pressure of other work made it impossible for me to do more than recognise the importance of the fossils as records of a Jurassic flora from a country which has afforded very little information in regard to Mesozoic Botany.

Probably the commonest type of foliage among the impressions of Carboniferous plants is one which simulates that of our living ferns. These palæozoic fronds were originally believed to belong to the true ferns, but recently some of them have been taken from this group and included in the Pteridospermeæ. There remain, however, a large number of fronds the true affinities of which are yet doubtful. Thus, though there are still a considerable number of species which belong to the ferns, the number of doubtful examples and of those now definitely known to be pteridospermous far exceeds the number of those attributed to the Filices. Indeed, we cannot now consider the latter group to have been dominant during the Carboniferous epoch.

In 1895 Professors Dewar and Fleming made an extensive and careful series of observations connecting temperature and the thermo-electromotive force of some twenty metals compared with lead. The greatest care was taken in the preparation for, and in the conduct of, the experiments, and about thirty readings, at temperatures ranging over the 300° between the boiling point of oxygen and the boiling point of water, were recorded for each metal. A full description of the mode of experimenting, with the results for each metal, was published in the Philosophical Magazine, July 1895. In their discussion of the results a further examination of them was promised, but has not appeared. Professor Fleming, however, in a Friday Evening Discourse at the Royal Institution in 1896, indicated that the lines of thermo-electric power did not appear as straight lines although they were approximately so.

The present paper deals with further investigations into the structure, the stratification, and the plant remains of peat deposits, carried on in various districts during 1907, 1908, and 1909.

The objects of the research, stated briefly, are to determine, as far as the state of preservation of the material permits, the history of the flora on peat-covered areas since their formation during the later stages of the glacial period. This really resolves itself into a research dealing with the changes in distribution undergone in post-glacial times by part of the British flora.

In February 1909 Mr John Thompson, Hull, forwarded to me for identification, along with species of Hydroids, specimens of a “Pedicellina,” which he was unable to identify with any known British form. These specimens proved to be of particular interest; and although a first consignment was dead on arrival in Edinburgh, Mr Thompson was successful in obtaining additional specimens, which, having travelled safely, were kept under observation in a living state for a week, when they were preserved for more detailed examination. Cocaine was found to be the most successful narcotising agent.

This paper discusses the effects of errors in linear and angular measurements on the accuracy of surveys.

It is necessary to state at the outset that, as the investigation is based on the theory of probability, the conclusions drawn are only advanced in the hope that they will serve as guides in practical surveying, and must not be taken as of rigid precision. Perhaps it is superfluous to state that there is no method of determining beforehand the error which will accumulate in any survey ; the utmost that can be done is to assign some mean value to the error which will serve as a useful criterion to which actual errors can be referred.