body weighs the same whether hot or cold is 

 almost sutficient to prove that heat is not a sub- 

 stance, since it has no weight. It was conclusively 

 shown by Kumford and Joule that heat is a form 

 of energy. Rumford, who was responsible for the 

 boring of cannon for the German army, deduced 

 that there was a relation between the amount of 

 energy expended in boring and the heat produced, 

 and Joule actually measured the numerical rela- 

 tion between heat and work. Light and heat, 

 therefore, are not substances, but forms of energy, 

 and from many experiments it has been concluded 

 that they are both wave motions. They can both 

 travel through a vacuum. This is known because 

 the sun's light and heat reach the earth, having 

 passed for over ninety millions of miles through 

 a vacuum. This fact may also be illustrated by 

 the apparatus used for measuring the sun's 

 radiant heat It consists of a thermometer with 

 a blackened bulb enclosed in a glass vessel free 

 from air. The bulb can be seen and the; tempera- 

 ture of the thermometer rises when the apparatus 

 is exposed to tlie sun, showing that both light and 

 heat pass through a vacuum. The passage of 

 these through space with the enormous velocity 

 of IStJ.fXK) miles per second is inconceivable 

 without some medium, and a mndium called ether, 

 which pervades all space, and in which the parti- 

 cles of ordinary substances move, has been 

 assumed for t'ae transmission of light and heat 

 from place to place. 



The next question to consider is how they pass 

 through this medium, and there is abundant 

 evidence to show that they travel in the form of 

 waves. The reasons for classing them as wave 

 motions are that we can get in light and heat 

 (a) reflection, (b) refraction, (c) interference. It 

 is interesting to note in addition that light and 

 heat can be polarised, and this shows that the 

 waves are transverse, i.e., are due to motions in 

 the ether at right angles to the direction in which 

 the light or heat is going. The only difference 

 between the waves of light and heat is the length 

 of the waves. Light waves are shorter and affect 

 the eye, whilst the heat waves are longer, the 

 lengths of the waves in both cases being extreme- 

 ly small. 



Numerous experiments were then shown, illus- 

 trating that light and heat can be reflected and 

 refracted, and that both follow the same laws. 

 For the experiments in heat a very delicate instru- 

 ment called the thermopile was used, and the 

 construction of this and the sensitive galvano- 

 meter, to which it was attached, were explained. 

 The radio- micrometer of Boys, and Langley's 

 bolometer were described, and it was mentioned 

 that these instruments would show an alteration 

 in temperature of one ten-thousandth part of a 

 degree centigrade. 



Thf* absorption of light and heat by various 

 bodies was next considered. It was shown that 

 the colours of bodies were due to their different 

 powers of absorptior. White light is made up of 

 seven colours : red, orange, yellow, green, blue, 

 indigo, and violet,andaredbody absorbs all these 

 colours except the red. A black body absoros all 

 the colours, and it was then shown that a black 

 body absorbs beat. Experiments on the different 

 absorptive powers of iodine dissolved in carbon 

 disulphide, alum, glass, and rock salt were per- 

 formed. Iodine solution was shown to be opaque 

 to light, but transparent to heat. Alum was 

 opaque to heat rays, but transparent to light. 

 Glass is an interesting substance, as it is trans- 

 parent to the light waves, i.e., the shorter waves, 

 but opaque to the heat waves, i.e., the longer 

 waves. Hence glass may be used for fire screens 

 and for covering greenhouses. Rock salt v as 

 transparent to both light and heat. 



In conclusion the sun's radiant energy was 

 referred to and Pouillet's pyroheliometer, an 

 instrument for measiu-ing the radiant heat of the 

 sun, was explained. The encrmous energy 

 possessed by the sun is a matter for speculation, 

 but of greater interest to mankind is how this 

 energy is kept up. Helmholtz considered that it 

 was due to a very slight contraction of the sun, 

 and thought that if the sun contracted one ten- 

 thousandth part of its volume it would supply as 

 much heat as it radiated during 2,000 years. 



A vote of thanks was given to the lecturer, and 

 in his reply Mr. Leeming acknowledged the help 

 he had received from Mr, Jeffs and the laboratory 

 assistants of the school. 



'NORMAN ARCHITECTURE IN EAST KENT CHURCHES." 

 By Mb. T. UNDERBILL, Jun. 



A most interesting lecture was delivered by 

 Mr. T. Underbill, jun,, to a rather small attend- 

 ance of members of the East Kent Natural 

 History and Scientific Society at the Be;iney 

 Institute on "VVednesdav evening, Mr. Sidney 

 Harvey, F.I.C., F.C.S., 'presided. The lecture, 

 which was illustrated with excellent lime-light 

 views (the lantern being manipulat-ed by Mr. A. 

 Lander), was most attentively followed, and gave 

 evident pleasure to the audience. 



In the course of his remarks, Mr. Underbill 

 said that if they left out the Norman por- 

 tions of thti Cathedral and the Monastic 



buildings (such as the Norman Staircase which 

 was considered to be a very fine specimen) they 

 found that there was not much work of the Nor- 

 man period left in the City churches. They could 

 discern remains of the Norman period in St, 

 Peter's.St.Alphege's.and St.George's. Dr. Cox(the 

 greatest ecclesiologist) advanced the theory that 

 the top tier of the celebrated font in St. Martin's 

 Church was a restoration of the Norman. Turning 

 to the parishes just outside the City they would 

 be struck by the many churches of Norman con- 

 struction sun-ounding them. St. Stephen's 

 Church afforded an example of an early 



