Ramsden, in his second effort to make an engine, was completely successful, insomuch that a sextant divided by it being subjected to the examination of Bird, was by him reported to be fit for every purpose of nautical astrono my. Bamsden's account of this engine was, in 1777, pub lished by the Board of Longitude, who rewarded his inge unity with the sum of 300/. For a further sum of 3151., he made over to the public the property of the engine it self, on condition, that at stated prices he should divide ally instruments that might be sent to him by other makers, so long as the engine should be allowed to remain in his pos ses,,ion.
to the account of Ramsden's being published, and befere its construction was generally known, Messrs Do!loud made an engine, differing materially we believe from the former ; but as it was never used except in the graduation of instruments made by them, the only judg ment we can form of its quality, arises out of the high re spectability of that well known house.
In the year 1778, the late Mr John Troughton complet ed a graduating engine, which at the full stretch of his pe cuniary means had occupied him for three years. In its general construction, this differs in no material respect from Ranisden's, though it is generally, we believe, thought to be superior in point of accuracy. The trade were so ill satisfied with Ramsden, on account of his keeping their work for an unreasonable length of time, as well as for the careless manner in which it was often divided by his assistants, that Troughton immediately, at augmented prices, found full employment for his ; and he has been heard to say, that by the care and industry of himself and his young brother, he soon found himself as well remune rated for making his engine, as Mr Ramsdell had been by public rewards.
It was about 1788, that Mr John Stancliffe finished a dividing engine. This accurate artist had been appren tice to Hindley of York, and for many years a foreman to Ramsden. The latter derived much information from him in the construction of his second engine, in which the cutting-frame of Hindley was adopted. In the first, the divisions were cut with the beam-compass, which, com pared with Hindley's apparatus, is tedious and inaccurate. Mr Stancliffe's practice has almost exclusively been con fined to making sextants, and their being held in the high est estimation, furnishes the most certain proof of the ex cellence of the engine by which they were divided.
It would be useless particularly to enumerate all the en gines that have been made for angular dividing ; perhaps there may be ten or twelve in London, generally copies of Ramsden's second engine. The greatest novelty that has appeared in this way, was given a few years ago by Mr James Allen, an industrious workman, which he stiles a self-correcting method of racking the plate, and which, with the usual good nature of the Society of Arts, Scc. was ho noured with their gold medal. Those who wish to know more of it, may, by consulting the journals of that Socie ty, gain full information, and have an opportunity to exa mine whether or not it deserves its title.
As in our article we have not room for more than the description of one circular engine ;—as Ramsden's has been copied into more than one work similar to our own ; and as that of the present Mr Troughton has not yet met the public eye, we give the preference to the latter, which at our request he has lately communicated, in the follow ing latter to Dr Brewster: Dear Sir. I remember that in a late conversation be tween us, you gave me to understand, that a description of my circular dividing engine would be acceptable to you, in order to form a part of the article in your Encyclope dia to which it belongs. For that purpose, I have at length drawn it up, not to my own satisfaction indeed, for I wish ed it to have been done well ; but such as it is I have the honour of presenting it to you.
The excellent engine of my late brother being fully four feet in diameter, gave to the operator, when at work near the centre, a position so painful, that it had done no good to either his health or my own, and had materially injured that of a worthy young man, then my assistant ; it was evi dent that, by making one of smaller dimensions, this evil would in a great measure be removed, and I foresaw that by employing my own method of original dividing, from which to rack the plate, a considerable reduction might he effected without any sacrifice of accuracy. I also per ceived, that by contriving the parts with more simplicity than Ramsden had clone, I could get through the work at less than two-thirds of the labour and expense.