Owing to the many improvements made in the designs, the use of better materials, 

 the application of specially designed tools and machinery, it is no longer necessary to 

 use large and heavy instruments. An instrument of about two-thirds the size and weight 

 of those made ten or fifteen years ago will now do the same class of work. It is by these 

 methods that lightness has been gained, and to them we must look for advances in the 

 future. Unless the size of an. instrument is decreased, the resistance of its exposed sur- 

 faces to wind pressure, causing sudden vibrations or tremor in the instrument, will of 

 necessity require a certain amount of weight to secure the needed steadiness, and if this 

 weight is not in the instrument proper, it will have to be in its tripod legs. This is 

 especially true in this era of high telescope powers and sensitive spirit-levels. What is 

 needed is that engineers and surveyors should have more confidence in instruments of 

 smaller size as made by the best makers. 



Wherever less weight is of great importance our patrons should not hesitate to order 

 our smaller Transits Nos. 2, 3, or 4, weighing 10^ and 5 Ibs. respectively, in preference 

 to a larger instrument made of Aluminum and divided to single minutes, but of equal 

 weight. These small instruments are just as durable and capable of doing just as close 

 work as the larger ones. Being made of a like metal throughout, whose coefficient of 

 expansion* is lower, they will retain their adjustments better than larger ones made in 

 whole or in part of Aluminum. Suppose an instrument is adjusted in-doors and im- 

 mediately is taken into the cold atmosphere of winter : other things being equal, if the 

 coefficient of expansion of some parts differ the adjustments will very likely be 

 deranged. Besides, the instrument being smaller, the boxes are likewise smaller, thus 

 reducing the weight and making it more portable at the same time. The same, in A 

 measure, can be said of the tripod, although it is against our convictions to use a lighter 

 tripod with a small transit than is used on the larger ones. 



The only exception to the above exists in the Telescope, which, of course, being 

 correspondingly shorter in a small instrument, will have a smaller aperture and less 

 power. However, to secure the same aperture and power for Transits Nos. 2 and 3 

 (No. 4 being inverting), as for our Transit No. 1, with an erecting eyepiece, it is only 

 necessary to order an inverting telescope to attain these conditions. 



There are other reasons why makers should be somewhat conservative in the adop- 

 tion of aluminum as a material for the finer class of surveying instruments, but as they 

 relate principally to the treatment of aluminum during construction: graduating 

 process, etc., they may be omitted here. In conclusion we wish to say that the future 

 developments in alloying it as a base with other metals or combination of metals, will 

 be watched by us with due care, and that whenever such developments will warrant 

 their adoption in the various parts of instruments, we will only be too glad to avail 

 ourselves of any superiority such alloys may possess. 



* The Ideal metal for a Surveying Instrument is that which has a coefficient of expansion equal to that of 

 its glass parts, so as to retain tJie adjustments in -varying temperatures. 



Coefficient of glass per linear foot, for i F. . 0.000054 inches. 



" steel ....... 0.000076 



" brass " " " 0.000125 " 



' aluminum per linear foot, for i F 0.000148 



Aluminum is farthest removed from the above requirements, steel or cast iron being nearest, and als 

 lighter and harder than brass ; and non-friction metals would be more generally adopted were it not for the uso 

 of the compass and the liability to rust in the field. 



Repair of Instruments. 



We are often applied to for correcting 1 new and repairing 1 old instruments made by other 

 makers. We will here remark, that as workmanship, material and construction of different 

 makers' instruments vary from one another, it is oftentimes impossible to repair them in an en- 

 tirely satisfactory manner without going 1 into an unwarrantably great expense, or without mak- 

 ing such alterations as would practically make a new one. We will always guarantee in such 

 cases to put the Instrument in as good order and adjustment as the character of its construction, 

 workmanship and material, the extent of damage and the general wear will permit, and that all 

 repairs are promptly and conscientiously made. The charges will be according to time con- 

 sumed, and as low as is consistent with good work. Parties sending 1 instruments should point 

 out in detail whatever parts they wish to have repaired ; but the best course to be pursued is to 

 have the instrument put in thorough order and adjustment, implying, as it does, that the firm 

 should make such warrantable repairs as will make it as serviceable as possible. This course is 

 always more expensive, but the most satisfactory to insure good work, and it is also the cheapest in 

 the end. Our own instruments, whenever practicable, should always be sent to us for repairs to 

 insure fullest satisfaction. Much time j?nd money is frequently saved by so doinsr, as we are in a 

 position to duplicate parts from stock on hand, fn sending an instrument to us from a distance it 

 should be carefully placed in its box and Ihen again in a packing box, as explained under " Trans- 

 porta'ion of Instruments," Part I., in order to conform to the rules of most of the large Express 

 Companies, which will admit it to single rates. 



