Show WHAT IS HEAT in abeso days of oppressive acm per aturo some people take a certain comfort in the knowledge that it is so and go many degrees while in others the knowledge of the figures intensifies the buffering there is a majority of people who leave not a clear conception of the various terms employed when heat and its degrees are spoken of and we are certain to depond to the wish of many if wo leave the mazes of poll lies for a day and tike an unimpeded stroll on the straight path science oci ence for thi purpose it is needful to clear the way of a few obstructions in the shape ot some prejudices or erroneous conceptions regarding the nature of heat kitcat is tho unknown cause of lie sensation of warmth and of a multitude of common cheno mena in nature and art in old times it was believed heat was some kind of a substance inherent in borno sorno articles more than in others and thus causing the difference of tern in them this is utterly wrong heat is neither more nor less than a form of motion a force not a matter this can bo proven because a heated body is never heavier than it was before heated whence heat is called i e not capable to be weighed and again themie of heat is disproved by the simple fact that it can be produced in any quantity without visible flame or combustion as when wo melt two pieces of ice by rubbing them together when the friction one mode of motion develops what we call heat an inherent force the most generel and notable effect which heat produces on matter is to expand it the length of a metallic bar varies with every change of temperature and it ever the same at the same temperature every blacksmith consciously or unconsciously ly applies thi law of expansion by beat and contraction by cold when he seta a tire on a wheel after having healed the iron licop to alip it on easily and letting it contract in cooling binding the felloes together with enormous heat in almost every kind of structure the expansion and contraction from changes of temperature must bo carefully guarded against particularly in the construction of iron bridges watches and clocks when not compensated go faster in cold weather and slower in hot an immediate consequence of the expansion or contraction of their balance wheels and pendulums if a flask full of water or alcohol be dipped anio hot water or held over a lamp a portion of the liquor runs over a class shell which floats in a vessel of water kinks to the bottom when the water is heated and aa water i healed the water continually rises lo 10 the surface if a bladder partly filled with air and lightly tied at the neck bo heated before a fire the contained air will expand and the bladder will bo distended As it cools it become flaccid again by des arces these homely examples are given to illustrate the general law by special cases known everybody there is however one great exception to abia law of expansion by hoat an contraction by cold water from centigrade or 33 fahrenheit at which ice begian to melt it contracts as the heat is increased up to cen higrade or about 40 F atter which it begin to expand like other bodie hence we say that water ia densest w hearit ft at 40 fahrenheit this ia a wisa arrangement of providence in cold weather as the surface water alike or river freezes to near centigrade it becomes heavier than the hotter water abdow and inks to the bottom this goes on till the whole lake has the of centigrade ti As the cooling proceeds further the water becomes light erand therefore remains at the surface till it is frozen did water not po this property a severe winter would freeze a lake to the bottom killing all organic life in it such as fish and the heat of summer might be insufficient lo 10 it all we have in the last paragraphs par made use of some terms as degrees centigrade fahrenheit which may bo strange to acme of our readers A no on hoat or temperature pera ture can be held without a perfectly of these terms we will close our with a brief explanation of the modern ascii method of measuring heat heal by tho thermometer beat measurer chaja an in consisting of a narrow glass tube of aa uniform a bore as possible A bulb ia blown on one end of tha tube large if the instrument ia meant to be very delicate small if a common instrument to be made this bulb is heated to expand the contained ponta ined and then the open end of tho tube IB plunged into alcohol dually tinged with coloring matter for greater visibility the bulb and part of the tube are filled with aa much of the alcohol aa Is necessary for the size and purpose and after all has been expelled by means of heat ing tho upper end of the tube is hermetically scaled and all that re mains to be done is the graduation of the instrument by which some ita information may bo given by ita indications water being one of tho most common bodies in nature and being everywhere easily obtainable n a stale af pf great purity Is employed ag a standard base of the ecale of temperature pera ture the and the boil ins of vatar familiar to everybody taken alii iho terminal points male the foi ncr is atzei tailed on tho thermometer by immersing the bull and the coition or the tube containing lie liquid in pounded which the malel portion it freely trickling nd wha the level af pf clr spirit has become citation ary ila position iff is marked pa the ube the bull jk in lie ira above iho hiiter s A V T S boiling by which operation we ob lain the point all that TO mains to be done u the numbering and subdividing tub dividing of this most generally used scale now there are three systems fahrenheit a german philosopher died in 1740 ascertained certa ined a lower point than that fixed by the two other systems and bis freezing point is 32 degrees below the others but ins freezing point i marked 32 and his boil ing point so that there is an interval of between his freezing point and boiling point reaumur a french physicist born feb 28 1683 died oct and celsius a swedish naturalist called the freezing point of water 01 but differed in the graduation the former dividing the distance up to the boiling point in ap while tho latter chose iho more convenient number whence his scale is commonly called england and america generally use fahrenheit scale F germany reaumur R and france helsius abut Cb ut the latter is uni venally occupied by the scientific moi of the world with these data it is easy to cons vert ono indication into iho other the following scale will afford a clear view of it fahr 32 77 reau 20 40 80 cent 25 50 freez boil much more might be said about boat the fundamental principle of all vitality and the indispensable companion of all motion and forces but our pace is more than exhausted we are afraid the patience of our readers also still some may have obtained information which they would have had to seek on a more circuitous path otherwise if so we are satisfied |