120 TIDB TABtR. 



»n<i so adjuste<5, that its dotted circle shall coincide with that 

 of thp same size in fig. 1. Underneath the waier a circular 

 piece of paper, about the same diameter as fi^;, 2, i» to be 

 placed, so that fig. 2, may move f.eely rouixd on its centre. 

 The oblong shaded spare in fig. 2 is to be cut out previously, 

 so that the name of the place, for which we want to find thfe 

 time of highwater, may appear through it. The table being- 

 thus put together, we have only to turn round tlie smaller cir- 

 cle, fig. 2, till the name of the place, for which we would know 

 the time of highwater, is seen through the aperture; when 

 the time for any given day will be s own by the part of the 

 hour-circle, fig, 2, that stands against the line of the moon's 

 age on that day. Thus for example, if 1 want to adjust 

 the table to Worthing, having turned the circle till Worth- 

 ' ing appears through it, I shall find, that, when the moon 

 is two days old, it will be high water there about five mi- 

 nutes before 12 ; when the moon is nine days old, about a 

 quarter after 6 ; and so for any other day. 



The difference of the length of the lines in the larger 

 circle points out the progressive increase and decrease of the 

 rise of the tide ; showing its comparative height, from the 

 spring tide, when it is the greate&t, being about 36 hour* 

 after new or full moon, at every place, to the neap, when it 

 is the least. Hence, if we know what is the general rise of 

 the spring tides at any place, we may calculate how high 

 the tide may be expected to flow at any given time of the 

 moon's age. 

 Table to show As it is obviously essential for finding the time of high 

 themoon'sage. ^ater to know the moon's age, a general table of lunations 

 is annexed. The use of it being sufficiently explained in 

 the table itself, all that is necessary for me to say is, that 

 the small shaded circle of fig. 4 is to be cut out, and fig. 3 

 to be cut out and put over it in the same manner as fig. 2 

 over fig. 1. 



For the gratification of such of my readers as might wish 

 to have these tables in a form for use, without taking the 

 trouble of copying them, or destroying the plate, I have 

 given a duplicate of it, which may be cut out and pasted on 

 a card. 



Hydrophilus will no doubt perceive, that! have taken the 



libert/ 



