1843.] On Artificial Fuel. 231 



terraced road to the nearest navigable river might be so constructed, as 

 to answer in the centre for locomotive carriages, the sides for channels 

 of irrigation. Steam engines at the heads of successive levels throw 

 up water; the terrace in this way if occasionally submerged, would 

 attain great hardness, in fact be silicified in course of time in all pro- 

 bability. All road-making should be done conjointly with facilities for 

 water ; the supply of the four months is ample for the twelve if retain- 

 ed, instead of being permitted to run waste, and carry off soil, filling 

 up rivers. 



A Companion to the Moon Table, by Capt. Shortrede, 1st Assis- 

 tant G. T. Survey. 



In order to have the times of true as well as of mean, new and full 

 moon, I have constructed the present as a companion to the moon 

 table, by means of which the corrections to be applied may be found 

 to be less than half an hour of the truth. 



The term syzygy (the same radically as 3J2RT conjunction) being 

 used to denote indifferently the conjunction of new or full moon, it is 

 obvious, that as at a syzygy the moon must be in line with the earth 

 and sun, the first correction of the mean to the true time will be that 

 arising from the unequal apparent motion of the sun in its orbit 

 depending on the sun's anomaly. This correction which at its 

 maximum is about 10 minutes more than 4 hours, may be taken at 

 once from the back of the card to within a few minutes of its true 

 amount. As the anomalistic year exceeds the tropical by 25m. 

 07.2s. and the Julian by 13m. 58.8s., the relative position of the two 

 circles on this card ought properly to be shifted by corresponding 

 quantities, amounting to about 1 day in 57-3 years in N. S., or 103 

 years in O. S. ; but as this can very easily be taken account of, I have 

 thought it unnecessary to provide for it by a moveable card. If the 

 moon table were provided with a vernier, or other means to admit 

 of being read with certainty and ease to within an hour, it might 

 be worth while to add here a moveable card; but for the present 

 these considerations give way to convenience. 



2 H 



