Mr. S. Whinery, Consulting Engineer, says that in most cities the data afforded by local past experience and results, furnish the best basis for future projects and programs. Unfortunately few cities have records of these. The head of the department usually relies upon his own memory or that of his predecessor. While the methods followed and results obtained in other cities may and should be studied, it must be borne in mind that it is not safe to base conclusions upon such data without a full knowledge and careful consideration of all facts and conditions affecting them. This is particularly true of reported cost data, for in addition to differing physical conditions, it is unfortunately true that the present methods of accounting in many street cleaning departments make it next to impossible to ascertain the actual or relative unit cost of the various details of the work, and intelligently to compare results in one city with those in another. The experience of the New York State Bureau of Municipal Information in seeking data from the fifty largest American and all New York State cities provides ample proof of this condition. Fifty were able to give some data, but of these only a few had any accurate and detailed cost statistics. The relative amount of dirt from the different sources of dust depends on the character of construction and condition of street surface, amount and character of traffic, character of neighborhood and people in the neighborhood, and street railway tracks. Street dirt is divided into two general classes: (a) Natural, and therefore unavoidable, and (b) that due to carelessness and therefore avoidable. In the first class are dust from the air, and dirt coming from the wear of pavements, vehicles, tires and horses’ shoes; excrement of animals, dirt and sand which work up through the joints of pavements, laid on earth or sand foundations and having sand or gravel joints; dirt brought in from adjacent unpaved or macadam streets, and leaves from shade trees. In the second class are soot, refuse swept from sidewalks, thrown from buildings and discarded by pedestrians, dirt dropped from overloaded vehicles and débris from construction operations. The real duty of the street cleaning department is the removal of the first class, but in doing so it is compelled also to sweep up and cart away the material in the second class. In order to reduce its operations as much as possible, it must, therefore, in cooperation with the police and health authorities do everything it can to prevent the accumulation of the avoidable material by enforcing ordinances and through the cooperation of the public in general. Contract vs. Municipal Cleaning