lviii INTRODUCTION TO THE MAKERSTOUN OBSERVATIONS, 1845 AND 1846. 
Giving the last result two values, we find, from both determinations, 
Proportion of whole heat stopped by glass plate A, =0-226. 
97. Besides the breaking of the cylinders by the freezing of the liquid, the 
instrument has been rendered useless for good experiments several times by the 
deposition of a brownish oily sediment, which finds its way into the thermometer 
tube, and this though the liquid had been long prepared by the maker. When this 
deposition of sediment occurred, the instrument was sent to the maker to be 
cleaned ; the observations, therefore, in this volume, are nearly unaffected by it. 
RAIN-GAUGES. 
98. The Observatory rain-guage is placed in a space, enclosed by a paling on 
the top of the Observatory hill, with a good exposure on all sides. The funnel-mouth 
is 6:1 inches in diameter, 8 inches above the soil, and 218 feet above the level of 
the sea. The quantity of rain is measured at noon by pouring it into a glass tube, 
graduated with reference to the aperture of the funnel. 
99. The monthly results of two other gauges are given in the abstracts. One 
is placed on the top of the greenhouse roof, 680 feet NNE. of the Observatory 
gauge ; the funnel-mouth is 6-7 inches in diameter, it is connected with a graduated 
tube within the greenhouse, it is 18 feet from the ground, and 192 feet above the 
level of the sea. This gauge is sheltered to the E. and NE. by trees, and its indica- 
tions are therefore less trustworthy, especially during easterly winds ; the amount of 
rain received in the funnel is also affected by the gusts of wind deflected from the 
sloping roof. The other gauge is in the middle of the Makerstoun garden, with a 
good exposure ; the funnel-mouth is 6:7 inches in diameter, is 6} feet above the 
soil, 171 feet above the level of the sea, and about 620 feet N by E. of the Obser- 
vatory gauge. The funnel is connected with a graduated tube. The greenhouse 
and garden gauges were observed by Mr Maccatt, the head gardener, the former 
daily, the latter monthly. 
VANES AND ANEMOMETER. 
100. The vane is placed on the north wall of the Observatory, and by means 
of a rod and geering-wheels it indicates the direction of the wind on a dial-plate 
within the building ; this vane (occupying the position W’ in the plan, Plate I.) was 
found too heavy for light winds, and the directions of these were estimated for some 
time from a ribbon-vane. On November 13, 1844, a vane was formed of four large 
feathers froma turkey’s tail, this vane was mounted on along and light fir-rod, which 
passed through the roof of the Observatory, and had an index attached to its lower 
extremity, which indicated the direction of the wind on a compass fixed to the ceil- 
