In summing up the different conditions of the Nitrate Bath which affect the development of the image, as many as _four_ might be mentioned, each of which gives a more rapid reduction than the one which precedes it. These are--the acid Nitrate Bath, the neutral Bath, the Bath of strongly fused Nitrate of Silver, and the Bath containing _Ammoniacal_ Nitrate of Silver, which is quite unmanageable, and produces an instantaneous and universal blackening of the film on the application of the developer. Greater intensity of image is commonly obtained in a Nitrate Bath which has been a long time in use, than in a newly mixed solution: this may be due to minute quantities of organic matter dissolved out of the Collodion film, which, having an affinity for Oxygen, partially reduce the Nitrate of Silver; and also to the accumulation of Alcohol and Ether in an old Bath producing a short and friable structure of the film. i. _Effect of Temperature on Development._--Reduction of the oxides of noble metals proceeds more rapidly in proportion as the temperature rises. In cold weather it will be found that the development of the image is slower than usual, and that greater strength of the reducing agent and more free Nitrate of Silver is required to produce the effect. On the other hand, if the heat of the atmosphere be excessive, the tendency to rapid reduction will be greatly increased, the solutions decomposing each other almost immediately on mixing. In this case the remedy will be to use Acetic Acid _freely_ both in the Bath and in the developer, at the same time lessening the quantity of Pyrogallic Acid, and omitting the Nitrate of Silver which is sometimes added towards the end of the development. Also in the case of films which are to be kept for a long time in a sensitive condition by means of honey, etc., the modifying influence of temperature must be observed, and the quantity of free Nitrate of Silver left upon the film be reduced to a minimum if the thermometer stands higher than usual. SECTION IV. _On certain Irregularities in the Developing Process._ The characteristics of the proper development of a latent image are--that the action of the reducing agent should cause a blackening of the Iodide in the parts touched by light, but produce no effect upon those which have remained in shadow. In operating both on Collodion and paper however there is a liability to failure in this respect; the film beginning, after the application of the developer, to change in colour to a greater or less extent over the whole surface. There are two main causes which produce this state of things:--the first being due to an irregularity in the action of the light; the second to a faulty condition of the chemicals employed.