350 New Outlines of Chemical philosophy. 



little gtim, the vernier is brought to zero, and the nut F turned 

 round till two adjacent faces of the crystal are at right angle to 

 the plane of the circle ; the mirror D is then turned round till 

 ou viewing any object by reflection, the image reflected by one 

 face of the crystal is coincident with that reflected by the mirror ; 

 then the mirror and one face of the crystal are parallel ; the 

 index (which of course carries with it the crystal) is next to be 

 moved, till another face of the crytal is brought parallel to the 

 mirror; the angle through which the index has been moved is 

 the supplement of the angle of the crystal. 



The advantages of this instrument are these : 1st, since when 

 the plane of the mirror and one face of tlie crystal are parallel^ 

 the two reflected images will be coincident, in what position so- 

 ever the eye be placed ; the goniometer may be held in the hand 

 when in use. 2d, As both the mirror and the crystal may l)e 

 adjusted with the utmost precision, and the coincidence of the 

 two images accurately observed ; the angle may be measured 

 very minutely. 3d, It is very portable. 



LXX X 11 . Nexu Out lines of Chem leal Philosophy. By Ezekiel 

 Walkeu, Esq. of Lynn, Norfolk. 



[Continued from vol. xlvili, p. 345.J 



J. HERE is scarcely a single operation of Nature that has beert 

 explained in such a manner as to meet with general approbation. 

 Electricity, combustion, respiration, animal heat, fixed caloric, 

 radiation of cold, composition of water, and various other objects 

 of physical inquiry, are supposed by philosophers in general to 

 be clearly explained; but conclusions in direct opposition to those 

 have been advanced by others. Now it is evident that either 

 cne or both of these explanations are erroneous, and therefore 

 terrestrial j)hysics cannot be ranked with the sciences. 



When an erroneous hypothesis is recorded in books of science 

 and taugiit by the most learned professors, few will be incline "l 

 to doubt of its truth. But the first step to knowledge is to doubt, 

 lie who never doubts never examines. And without examina- 

 tion erroneous opinions may be handed down from one genera- 

 tion to another, if not detected by what is called chance. 



Let us not, therefore, follow those who, from habit, indolence, 

 or the fear of singularity, are the determined supporters of old 

 eatablished opinions ; but examine those opinions with due care, 

 and then mark the progress of future discoveries. 



In the investigation ef problems in terrestrial physics, it is r^e- 

 ccssary to observe, that there arc ccr:a:.n invisible, imponderabk-, 



untangible 



