Jit Portable Telegraph. — Scientific Newt. 



have good reafon to aflert, that there do not commonly occur above eight or ten days in 

 the year when intelligence might not be conveyed by land. 



If . eight men were pofted at each permanent ftation, at the diftance of eighteen or 

 twenty Englifh miles afunder, with machines of twenty-five feet high, in h.izy weather they 

 might detach two men with portable Telegraphs, to the diftance of about fix miles from 

 each Nation, who, with eight foot Telegraphs, could keep up a regular communication. 



The portable Telegraph refembles that which I have defcribed ; it differs only in two 

 circumftances : for convenience, as it is fmall, and does not oppofe much furface to the 

 wind, it may be diftehded with ribs of wood inftead of cords. 



The portable Telegraph which my fon had the honour of fliowing to his Royal Highnefs 

 the Duke of York in Kenfington gardens, in Oftober laft, was furniflied with filken cords, 

 on purpofe to fhew how my larger Telegraphs were conftrufted ; but it was intended 

 merely for reconnoitring near an arniy, and was only fix feet high. 



In the eflay which the Academy has already received, I faid that imitations without end 

 might be made of my Telegraph. Every index or pointer that moves circularly, dividing 

 an imaginary circle into parts, and denoting figures or figns that correfpond with a voca- 

 bulary, is founded on the fame principle as mine. The French have laid afide their former 

 clumfy apparatus, and have conftrufted a Telegraph on thefe principles ; and the Admi- 

 ralty in England have, as I am informed, very lately done the fame. 



The firfl; pointers I employed in 1767 were windmill fails. I then tried indexes of the 

 (hape (fig. 5.) Fig. 8. A pointer, like a fword-cutler's fign, was recommended to me by 

 a member of the Academy, as a fecond or additional hand to move on the fame centre 

 as the principal hand. But a triangle, whofe bafe is equal to half its fide, is, of all the 

 figures I have tried, the moft diflindt. 



The Night Telegraph remains ftill to be defcribed ; its ufes are perhaps more extenfive 

 than thofe of the Telegraphs I have already publiflied ; and I propofe to make it the fubjeiSk 

 of another paper upon a future occafion. 



The art of conveying fwift and fecret intelligence is not one of thofe inventions which 

 attracts attention only by its novelty ; on the contrary, I am convinced that it will be 

 thought more valuable, the longer it has been fubmitted to the teft of time and experience. 



SCIENTIFIC NEWS, AND ACCOUNT OF BOOKS. 



Copenhagen, y/^/_y 12, 1798. 



T, 



H E Royal Society has propofed the following Prize Queftions. The Prize for each 

 is a Gold Medal, value one hundred rixdollars (22I. los.) 



I. Hijlory. What nations difcovered America before the Norwegians, and performed 

 voyages by fea to this part of the globe ? How far did the Norwegians extend their difco- 

 veries in America, particularly to the fouthward ? What conclufions may be deduced on 

 thefe points, either from decifive reafons or fimple conje£lures, from the writings and 

 monuments which flill fuBfift, fuch as forts, buildings, languages and traditions ? 



II. Mathematics. To find the funftion of all the quantities, which ferve conjointly to 

 determine the magnitude of the calorific efie£t of every combuftible material in common 



ufe i. 



