LAB 



LAE 



after the acid is once well formed, when 

 the serous part of the milk reddens vege- 

 table blues, no more is obtained by evapo- 

 ration and crystallization. Scheele ob- 

 tained this acid by the following process : 

 he evaporated sour whey to one-eighth 

 of its bulk, and then filtered it to separate 

 the coagulated cheesy matter. He then 

 added lime water to precipitate the phos- 

 phate of lime, and diluted the liquid with 

 pure water. He next precipitated the 

 excess of lime by means of the oxalic acid, 

 and then evaporated the solution to the 

 consistence of honey, poured on a quan- 

 tity of alcohol, which separates the portion 

 of sugar, of milk, and other extraneous 

 matter, and dissolves the lactic acid, and 

 distilled the clear filtered liquor till the 

 whole of the alcohol employed be driven 

 off: what remains is the lactic acid. This 

 acid is never crystallized, but always ap- 

 pears in the form of a viscid mucilaginous 

 substance ; it has a sharp taste ; it red- 

 dens tincture of turnsole ; and gives a 

 reddish shade to the syrup of violets. It 

 combines with alkalies, earths, and metal- 

 lic oxides ; and forms with them lactates. 



LACTUCA, in botany, lettuce, a genus 

 of the Syngenesia Polygamia JEqualis 

 class and order. Natural order of Com- 

 positse Semiflosculosx. Cichoraceae, Jus- 

 sieu. Essential character : calyx imbri- 

 cate, cylindrical, with a membranaceous 

 margin ; receptacle naked ; seeds even, 

 with a simple stipitate down. There are 

 eleven species, of which L. sativa, the 

 common garden lettuce, with its several 

 varieties, are too well known to need a 

 particular description. 



LACUNAR, in architecture, an arched 

 roof or ceiling, more especially the plank- 

 ing or flooring above porticos and piazzas. 



LADDERS, seating, in the military art, 

 are used in scaling when a place is to be 

 taken by surprise. They are made several 

 ways ; sometimes of fiat staves, so as to 

 move about their pins and shut like a 

 parallel ruler, for conveniently carrying 

 them : the French make them of several 

 pieces, so as to be joined together, and to 

 be capable of any necessary length: some- 

 times they are made of single ropes knot- 

 ted at proper distances, with iron hooks 

 at each end, one to fasten them upon the 

 wall above, and the other in the ground; 

 and sometimes they are made with two 

 ropes, and staves between them to keep 

 the ropes at a proper distance, and to 

 tread upon. When they are used in the 

 action of scaling walls, "they ought to be 

 rather too long than too short, :;nd to be 

 given in charge only to the stoutest of 

 the detachment. 



The soldiers should carry these ladders 

 with the left awn passed through the se- 

 cond step, taking care to hold them upright 

 close to their sides, and very short below, 

 to prevent any accident in leaping into 

 the ditch. The first rank of each division, 

 provided with ladders, should set out 

 with the rest at the signal, marching re- 

 solutely with their firelocks slung, to 

 jump into the ditch ; when they are ar- 

 rived, they should apply their ladders 

 against the parapet, observing to place 

 them towards the saliant angle rather than 

 the middle of the curtain, because the 

 enemy has less force there. Care must 

 be taken to place the ladders within a 

 foot of each other, and not to give them 

 too much nor too little slope, so that they 

 may not be over-turned, or broken with 

 the weight of the soldiers mounting upon 

 them. The ladders being applied, they 

 who have carried them, and they who 

 come after, should mount up and rush 

 upon the enemy sword in hand ; if he 

 who goes first happens to be overturned, 

 the next should take care not to be thrown 

 down by his comrade ; but on the con- 

 trary, immediately mount himself, so as 

 not to give the enemy time to load his 

 piece. The success of an attack by 

 scaling is infallible, if they mount the 

 four sides at once, and take care to shower 

 a number of grenades among the enemy, 

 especially when supported by some gre- 

 nadiers and picquets, who divide the at- 

 tention and share the fire of the enemy. 



LADEN ; the state of a ship when she 

 is charged with a weight or quantity of 

 materials equal to her tonnage or burthen. 

 If the goods with which she is laden be 

 extremely heavy, her burthen is deter- 

 mined by the weight thereof; but if light, 

 she carries as much as she can stow for 

 the purposes of navigation. As a ton in 

 measure is generally estimated at 2000 

 pounds in weight, a vessel of 200 tons 

 ought accordingly to carry a weight equal 

 to 400,000 pound's ; therefore, when the 

 matter of which the cargo is composed is 

 specifically heavier than the water in 

 which she floats ; or, in other words, 

 when the cargo is so heavy that she can- 

 not float high enough with so great a 

 quantity of it as her hold will contain, a 

 diminution thereof becomes absolutely 

 necessary. 



LAET1 A, in botany, so namedfrom John 

 de Laet of Antwerp ; a genus of the Poly- 

 andria Monogynia class and order. Natural 

 order of Tiliaceze, Jussieu. Essential cha- 

 racter ; calyx five-leaved ; corolla five-pe- 

 talled, or none ; fruit one-celled, three 

 cornered ; seeds with a pulpy aril. There 



