On the Level of the Sea. 341 



These experiments tend to confirm the opinion given out by 

 Franklin on this subject, in 1761. " If some rivers," says he, *' 

 empty themselves into lakes, without the latter ever overflowing 

 their banks, it is because the water is then spread out under so 

 large a surface, that there is daily removed by evaporation a mass 

 of liquid about equal to that which flows in. But there are rivers 

 which, from the extent of their course, and the breadth of their 

 mouth, may be compared to lakes. To complete the resem- 

 blance, it would only be necessary that a dike should stop the 

 course of the water, and prevent it from being emptied into the 

 sea. There would then occur some differences of level, accord- 

 ing to the seasons ; but in general, under certain circumstances, 

 these diffTerences would be confined within narrow limits. Al- 

 though the communication between the river and the sea be 

 open, it may be supposed that the dike of which we have been 

 speaking, really exists in the surface of junction of the fresh 

 water and salt water. Only this dike would be moveable ; it 

 would ascend a certain number of miles with the tide, and after- 

 wards descend. The extent of the excursions would vary with 

 the volume of the water. In some cases, we might also ex- 

 pect to find the sea water, and that of the river, mingled 

 together on meeting, and this to a greater or less extent, from 

 the twofold eff*ect of their motions, and of the diff'erence of their 

 specific gravities ; but at a certain distance from the mouth, the 

 fresh water, first carried down by the current, and again thrown 

 back by the tide, would oscillate nearly within the same limits, 

 without even reaching the sea. An ignorant person would ima- 

 gine that the water flowed off*, and^was partly lost through 

 some crevices in the earth, while in reality it is by the air that 

 it escapes. 



On the Rocks that afford the Gold Dust or Gold Sand met with 



in Rivers. 



As gold-dust or sand is met with in several of the river- 

 districts in Scotland, we think the following observations will 

 interest those who may amuse themselves in search of gold in 

 this country. 



