150 History of Mechanical Inventions and 



rived at the Admiralty, having landed at Peterhead in Scot- 

 land, and travelled to London by land. 



During this voyage only two men were lost, — one perished 

 oy disease, and one was drowned. The rest of the crew of 

 both vessels returned in perfect health and spirits. 



The plants collected during the expedition, have been put 

 into the hands of Dr Hooker for examination ; but we under- 

 stand that they do not contain any thing very new or im- 

 portant. 



We look forward with much anxiety to the publication of 

 the meteorological and magnetical observations taken during 

 this expedition ; particularly as they were made at a place in- 

 termediate, both in longitude and latitude, between Melville 

 Island, and the stations of Winter Island, and Igloolik. 



Art. XXIX.— HISTORY OF MECHANICAL INVENTIONS AND 

 PROCESSES IN THE USEFUL ARTS. 



1. Description of the Double Weather Sluices inventedby Robert TH0M,Esq., 

 Rothesay. Communicated by the Author. 



This apparatus is, to a certain extent, similar to the one last described : but 

 it has a double operation, the sluices first opening, one after another, as the 

 streams increase, until they reach a given height ; and then shutting, one af- 

 ter another, as they continue to rise above that height. Again, when the 

 streams begin to fall, the sluices open, one after another, until they (the 

 streams) fall to a certain point, and then again shut, one after another, as 

 they continue to fall below that point ; the same continuous rise in the 

 streams, first opening, and then shutting all these sluices in succession ; 

 and, in like manner, the same continuous fall first opening and then shut- 

 ting them in succession- 



This apparatus, in whole or in part, may, by a judicious adaptation, be 

 applied to many useful purposes, as will be readily perceived by such as 

 are conversant in these matters ; but the object chiefly in view in contriv- 

 ing it, was its application to what are termed, " Compensation Reser- 

 voirs." 



Suppose, for instance, that it is necessary to form a reservoir in the site 

 of some rivulet or stream, for the purpose of collecting water for some im- 

 portant object, and which water is to be carried away in a direction diffe- 

 rent from the natural course of the rivulet, it is evident that the proprie- 

 tors of land, or works on the rivulet, below where the proposed reservoir 

 is to be made, will object to its formation, unless some compensation be 

 made them for the water thus to be carried away. There may be many 



