Intelligence and Miscellaneous Articles. 303 



It does not appear to have been ascertained whether this substitution 

 occurs with the hydrate of lime as existing in mortar or cements, or 

 whether the water of the hydrate is retained, and a hydrated carbonate 

 consequently formed, in the induration of mortar. If, however, as is 

 perhaps most probable, the combined water in mortars is replaced by 

 the carbonic acid, agreeably to Sir H. Davy's statement respectmg the 

 hydrate of lime per se, the action which must be going on dunng this 

 exchange of principles, may of itself tend to the production of stalac- 

 titical incrustations. Upon the whole, therefore, it may safely be m- 

 ferred, that no conclusion unfavourable to the quality of the mortar 

 used in the erection of Waterloo Bridge, can fairly be deduced from the 

 existence of calcareous incrustations on the soflStes of the arches of 

 that structure. The tendency to the production of stalactites, how- 

 ever, in such situations, renders attention to the means of carrying off 

 the surface water from the superstructures of arches and vaults, addi- 

 tionally important ; as the amount of drainage consequent on the im- 

 perfection of those means, might, in the course of time, impair the 

 stabilitv of the arches, by constantly extracting lime from the mortar. 

 Wherei however, the obvious means of doing this are well employed, 

 as they doubtless have been in the construction of Waterloo Bridge, 

 no danger can be apprehended from the process by which stalactites 

 are formed. 



March 28, 1832. E.W.B. 



NEW LAMP. 



In the course of the first meeting, at York, of the British Associa- 

 tion for the Advancement of Science, the Rev. Wm. Vernon Har- 

 court, on the 1st of October last, showed a lamp constructed upon 

 a new principle, and explained the principle and construction of it : 

 he gave it the name of an oil gas lamp; not because it was lighted 

 by gas formed at a temperature below that of flame, (for this was 

 common to all lamps,) but because, as in the gas-lights of the streets, 

 the gas issued from a reservoir, and owed the perfection of its com- 

 bustion not to an ascending current of hot air, but to the force with 

 which it was propelled from the reservoir and carried the air along 

 with it. It differed, however, from the common gas-lights in these 

 circumstances:— that the reservoir formed part of the burner ; that 

 the gas was formed as it was consumed ; and that it was propelled, 

 not by a vis a tergo, and in a state of condensation, but by the ex- 

 pansive force of its own heat. In consequence of this circumstance, 

 the current of the gaseous jet was more rapid in proportion to the 

 quantity of matter contained in it than in the common gas-lights, 

 whilst it was also at a much higher temperature, so that it could 

 issue with a greater velocity without being liable to blow itself out. 

 The practical difficulty of the construction consisted in the obtain- 

 ing a steady supply of oil, especially with the cheap oils. Tins dif- 

 ficulty had been in a great measure surmounted ; but the instrument 

 was still imperfect, and had been charged by some accident that 

 evening witli a vegetable oil, from which a clear ligiit could not be 

 obtained.— Hr5< Report of the British Association Jhr the Advance- 

 ment of Science. 



