60 



FARMERS' REGISTER 



[No. I. 



Bridge, and probably in any other town. It 

 would be found very useful in other operations, 

 6iich as levelling the foundations for buildings, 

 conducting races lor waterworks, or in ditching 

 and draining. It is a tin tube about three and a 

 half feet in length, and three-fourths of an inch 

 in diameter, closed at each end, with a socket af- 

 fixed at right angles to ihe centre, for receiving a 

 moveable staff, similar to a surveyor's. At each 

 end of the tube, and communicating internally 

 with it, are two upright tubes or sockets, two and 

 a half inches long, of the same diameter, in each 

 of which is inserted with rosin or some other ad- 

 hesive substance, a small vial divested of its bot- 

 tom, and furnished with a cork tied by a string to 

 the neck, to stop it when filled with fluid, thus 

 preventing its spilling when the level is moved. 

 When the operator is to proceed to level a piece 

 of ground, the tube should be filled through one 

 of the vials with some fluid slightly colored; and 

 having fixed his staff, and placed the level on it, 

 he will uncork the vials, when the fluid in them 

 will find a level by having a free communication 

 through the tube, and the two uprights in which 

 the vials are inserted. His assistant will be fur- 

 nished with a ten-foot rod, graduated with feet and 

 inches, which he will place at the head of a gully 

 or other point where the levelling is to commence, 

 in front of which he will place a piece of paper, 

 which he will move up or down on the rod by di- 

 rection of the leveller, until the top of the paper 

 ranges with the top of the fluid in the vials, notinir 

 the elevation from the earth on the rod. He will 

 then step eight or ten paces, or measure. two 

 lengths of the rod on the earth along the course 

 proposed to conduct, the levelling, and elevating it 

 to a perpendicular, he will move it up or down hill, 

 until the paper placed at. the former elevation 

 ranges with the top of the fluid in the vials. The 

 leveller can, with great ease, move his level to 

 range Avith the rod, by placing his thumbs on the 

 mouths of the vials, and gently turning the sock- 

 et on the staff. If it be wished to give a fall or 

 rise of two inches in every twenty feet, it will be 

 readily done by placing the paper two inches 

 higher or lower on the rod, at each removal. In 

 conducting a long level, if it becomes necessary to 

 remove the station of the leveller, the assistant 

 should keep his rod unmoved at his last station, 

 and the leveller should advance beyond him to 

 any suitable position, and sight back to him, con- 

 tinuing the same process as in the commencement. 

 I would make the assistant carry on his arm a 

 basket of small sticks, to mark each station of his 

 rod, instead of employing an additional hand as 

 proposed by IM, N. After the line of level is run, 

 the situation of the sticks may be altered at plea- 

 sure, so as to produce proper curves, to be follow- 

 ed by the ploughman, who will be accompanied 

 by the leveller, to direct him, and pick up the 

 sticks. 



In levelling the foundation of a building, the 

 level is fixed near to it, and the assistant places the 

 end of his rod in a perpendicular position, at any 

 given corner, of the desired height or depth, noting 

 the number of feet and inches where his paper 

 ranges with the fluid in the vials. He then places 

 his staff at another corner, and the range of the 

 top of the water in the vials will immediately in- 

 form him whether it be too high or too low, and 

 by how many inches. 



In levelling- either up or down a stream to as- 

 certain its fall, the assistant places his rod at the 

 water's edge, and the leveller goes forward a con- 

 venient distance, sighting back to the rod-man, 

 who notes the height from the water, in a column 

 headed "back sights.'''' The rod-man then goes for- 

 ward in advance of the leveller, who makes a for- 

 ward sight, the height of which is also noted un- 

 der a separate column, headed "forward sights." 

 The leveller then moves his station, sighting back 

 to the rod-man, which is noted as above, who 

 then moves forward in advance of the leveller, 

 and so on alternately, until the levelling is com- 

 pleted, taking care to commence with a back 

 sight, and end with a forward one. The back 

 and forward sights will be equal in number, and 

 after adding up the feet and inches, in each column 

 separately, and deducting the smaller amount 

 from the larger, the difference will be the amount 

 of the fall. If the levelling be up stream, the amount 

 of the back sights will be the larger. The re- 

 verse takes place in levelling down stream. The 

 merest tyro in the science of engineering would 

 probably laugh at this communication: but it may, 

 nevertheless, be of service to somebody, in which 

 event my purpose is fulfilled. 



May 17th, 1835. 



SURFACE MANURING. 



To the Editor of the Farmers' Register. 



The urbanity and scientific research displayed 

 by your correspondent W. B., in his criticisms on 

 my remarks upon J. B's. communications, de- 

 serve a very respectful notice. He seems to pos- 

 sess a share of chemical knowledge to which I 

 have no pretensions; and I shall therefore offer 

 little more in reply, than such objections and diffi- 

 culties as present themselves to my mind, in op- 

 position to his opinions and arguments. 



His first observation in regard to the hypothe- 

 sis which I ventured to suggest, does not appear to 

 me to militate against it. I was well aware of 

 the truth which he states, that "chemical affinity 

 only acts at insensible distances;" and that "the 

 better the mixture of any two things having a 

 chemical affinity, one for the other, the more ra- 

 pid and perfect their combination." Now it is 

 equally true, according to my hypothesis, that 

 nothing which constitutes the food of plants can 

 combine with the earth, until such substance or 

 substances be dissolved in water. But the water 

 will dissolve them quite as soon while lying on, as 

 under the surface of the earth, by percolating 

 through the manure; for in both cases this water 

 must at an "insensible distance" from that which 

 it dissolves. The only doubt then seems to be, 

 whether, if the solution takes place below the 

 surface, the food which it contains for plants will 

 not be carried lower into the earth than it ought 

 to be: whereas, when it is absorbed from the sur- 

 face, it will go no deeper than nature intended it 

 should. As to there being "no gas in the earth," 

 W. B. is right in supposing I did not mean to say 

 so, however my language — never very accurate, 

 mighthave justified the inference. But my belief is, 

 that the greater portion, if not all of those gases 

 which constitute the food of plants, is imparted tq 



