2o8 THE NATURAL HISTORY 



also contribute to promote science : an obelisk in a garden 

 or park might be both an embellishment and an heliotrope. 



Any person that is curious, and enjoys the advantage of 

 a good horizon, might, with little trouble, make two 

 heliotropes ; the one for the winter, the other for the 

 summer solstice : and these two erections might be con- 

 structed with very little expense ; for two pieces of timber 

 frame-work, about ten or twelve feet high, and four feet 

 broad at the base, and close lined with plank, would 

 answer the purpose. 



The erection for the former should, if possible, be placed 

 within sight of some window in the common sitting 

 parlour ; because men, at that dead season of the year, are 

 usually within doors at the close of the day ; while that for 

 the latter might be fixed for any given spot in the garden 

 or outlet : whence the owner might contemplate, in a fine 

 summer's evening, the utmost extent that the sun makes 

 to the northward at the season of the longest days. Now 

 nothing would be necessary but to place these two objects 

 with so much exactness, that the westerly limb of the sun, 

 at setting, might but just clear the winter heliotrope to the 

 west of it on the shortest day ; and that the whole disc of 

 the sun, at the longest day, might exactly at setting also 

 clear the summer heliotrope to the north of it. 



By this simple expedient it would soon appear that there 

 is no such thing, strictly speaking, as a solstice ; for, from 

 the shortest day, the owner would, every clear evening, see 

 the disc advancing, at its setting, to the westward of the 

 object; and, from the longest day, observe the sun retiring 

 backwards every evening at its setting, towards the object 

 westward, till, in a few nights, it would set quite behind it, 

 and so by degrees to the west of it : for when the sun 

 comes near the summer solstice, the whole disc of it would 

 at first set behind the object : after a time the northern 

 limb would first appear, and so every night gradually 

 more, till at length the whole diameter would set north- 

 ward of it for about three nights ; but on the middle night 

 of the three, sensibly more remote than the former or 

 following. When beginning its recess from the summer 



