Iviii 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 unafi'ected 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 tree;*, and its indica- 

 tions are therefore less trustworthy, especially during easterly winds ; the amount of 

 rain received in the funnel is also afi'ected 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 Gi 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 obsei-ved by Mr Macgall, 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 from a turkey's tail, this vane was mounted on a long 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- 



