Aug. 10, 1888.] 



SCIENTIFIC NEWS. 



129 



SUN-DIALS, AND HOW TO MAKE 

 THEM.— I. 



A CONSIDERABLE number of books were written 

 during the last century on the art of " dialling," or 

 " dialing," as it was then spelt ; but if that word had 

 been used as the title to this paper, it is probable that 

 not one reader in a dozen would have guessed its mean- 

 ing without a glance at the columns below. 



"What an antique air," says Elia in his essay on 

 " The Old Benchers of the Inner Temple," " had the now 



almost effaced sun-dials, with their moral inscriptions, 

 seeming coevals with that great Time which they 

 measured, and to take their revelations of its flight im- 

 mediately from heaven, holding correspondence with the 

 fountain of light ! What a dead thing is a clock, with 



Fig. 



Fig. 3. 



its ponderous embowelments of lead and brass, its pert 

 or solemn dulness of communication, compared with the 

 simple altar-like structure, and silent heart-language of 

 the old dial ! It stood like a garden god of Christian 

 gardens. Why is it almost everywhere vanished ? " 

 Not only have most of the old dials vanished, but very 



few new ones are being made. Where a century ago 

 every skilled mason was expected to know something of 

 the art, for a regular art it was, we should now have 

 considerable difficulty in finding anyone but a mathema- 

 tician who could design the simplest sun-dial. The art 

 was surrounded with no little mystery, and often with a 

 good deal of needlessly involved calculation. The 

 treatises on dialling went, as a rule, into the geometry of 

 the subject, and when this included the consideration of 

 general cases, recourse was had to spherical trigono- 

 metry, and the refinements of the art need a certain 

 knowledge of astronomy. 



A sun-dial, as a rule, is only adapted for use in the 

 latitude for which it is constructed, and for this reason 

 they cannot be made by the thousand, and the only form 

 in which such a timekeeper can be obtained is that of a 

 small, complicated, and rather expensive " universal " 

 dial at the shop of an optician. Anyone who desires to 

 have a dial painted on the wall of his house, or on the 



tower or porch of a church, would have a considerable 

 difficulty in finding a workman who could do it. 



The following instructions, it is hoped, will render the 

 art of sun-dial making both intelligible and interesting ; 

 and a carefully made instrument, which will show the 



correct time to within two or three minutes, might be 

 both a useful and beautiful object in the humblest garden. 

 Two motions of the earth have to be considered. 

 First, the perfectly regular revolution of the globe on its 

 axis once in 24 hours. A circle being divided into 360 

 degrees, the earth moves through 90 degrees or a right 

 angle in 6 hours, and through half a right angle in 3 



