VOL. XLIII.] PHILOSOPHICAL TRANSACTIONS. 31 



where alike ; unless you find it requisite to give more force to one side than the 

 other, which these two screws will put in your own power. 



The press opens again, by a stroke or two of the hammer, the contrary way, 

 on the shoulders of the screws : and then you will find a true and fair picture 

 neatly printed off ; which, if any deficiencies appear, you may easily repair, when 

 dry, with a hair-pencil, and a pen, and a little of the same colour. 



If your paper does not soak in the moisture well, by being over-sized, it is ne- 

 cessary to wet the flannels, or the paper will not come off strongly enough co- 

 loured : and if the relievo of your medal be very high, it is best to put a little 

 cotton immediately on the back of the paper, between that and the flannels, that 

 the paper may be duly pressed into the deep hollows of the wax mould. 



This method is very easy and ready for taking the picture of a medal in any 

 colour : but if you desire a relievo only, without any colour, the way is much 

 shorter ; for nothing then is necessary, but to place a piece of card, or white 

 pasteboard, well soaked in water, on the wax mould, without any colouring, and 

 letting it remain in the press a few minutes, the business is done at once. 



Observations on the Manna Persicum. By John FolhergiU, M.D. London. 



N° 472, p. 86. 



In this paper Dr. F. endeavours to show that the ancient Greek physicians were 

 unacquainted with manna, as an article of the materia medica; and that if the 

 Arabians were not the first who introduced that substance into medicine, they at 

 least rendered the use of it more common and extensive. He then states that 

 the Arabians had 3 sorts of the drug, known by the names of manna, teren-jabin, 

 and ciracost ; that the manna Persicum is gathered from a prickly shrub called 

 alhagi, and is the teren-jabin of the modern Arabs. This manna is much infe- 

 rior to the Calabrian manna, which exudes from a species of fraxinus. This last 

 is the manna ofHcinarum, with the description of which this paper concludes. 



Cyanus Foliis radicalibus partim integris, partim pinnatis, Bractea Calycis ovali, 

 Flore iulphureo ; per Albert. Halter, Prof. Anat. et Bot. Gottingens. R.S. 

 Jng. et Suec. S. descriptus* N° 472, p. 94. 



Concerning the Propagation and Culture of Mushrooms. By the Rev. Roger 

 Pickering, V.D.M. of Deptford. N° 472, p. 96. 



The rains having thrown up on his mushroom beds a great quantity of those 

 plants, Mr. P. adds the following additional observations to those printed in these 

 Transactions, N°47l. 



* This plant is the Centaurea orientalis of Linneus. Centaurea cali/cibtu Kariotis ciliatis, folii* pin- 

 natifidis, pinnU lanceolatis. 



